I just want to bump this up so that others will see it and weigh in (no pun intended)...

I am no help, we have Britax Boulvard and a Britax Advocate and we love it. I drive a small car , Toyota Echo hatchback = yaris older version, and it still fits. My DS is 4 yrs old and he probably will outgrows the Britax within a year, just right in time to pass it on to his sister.
I also live in Northern Canada, so having a warm carseat is a plus over here.

My husband drives a Honda Civic coupe, so not only does it mess with front seat positioning, but it's hard for him to get our son in/out. He actually has to ask him to climb in (which he does). It will be extra bad with baby #2 because the seat won't be in the middle anymore...

Front-facing, our Britax seats would be fine - it's rear-facing that's the problem.

My husband drives a Honda Civic coupe, so not only does it mess with front seat positioning, but it's hard for him to get our son in/out. He actually has to ask him to climb in (which he does). It will be extra bad with baby #2 because the seat won't be in the middle anymore...

Front-facing, our Britax seats would be fine - it's rear-facing that's the problem.

Why do you want it to be in the middle? I have a 4 seater, and there is no middle, so it can not be put t in the middle in my car. My husband car Toyota Matrix could be put in the middle, but it is so much harder to take in an out the kid if he is in the middle. Move it to the either side, and maybe you will be pleasantly surprised how much easier it gets.

We tried putting it on the side, and it interferes with the front seat (whichever seat it's behind) even more, and it blocks all access to the back seat on that side. As such, my husband would have to get in not just in the closest seat but all the way in the middle. There's basically no way he could do that if there were a seat on the other side, even front-facing.

For the record, I'm not the one who wanted a coupe! I knew we would have this problem, but he really wanted the coupe instead of the sedan.

We decided not to do the convertible seats after seeing them in person. My husband has a 2-door sports car (Acura RSX similar to your Civic Coupe), and there is NO WAY one in rear-facing position would be comfortably usable for an infant in his car. Plus, I really wanted to be able to take the infant seat out and put it in the stroller, use it as a place for him to nap when we're visiting, quick way to move sleeping baby into grocery carts, etc.

We ended up going for the Chicco Keyfit 30 with 2 bases.

Oh yeah, with the infant seat it was no problem. We used one until our son was about 6 or 7 months old, then he got too heavy to be lugging around in the carrier (~22 lbs at 6 months). I suppose we could try to continue using it in the Civic until the new baby is front-facing. Our 22-month-old is maybe 28.5 lbs (weight limit is 35 lbs), but he is too tall for the seat (height limit is 32", which he passed a long time ago), so if the new baby is also tall, we might not be able to.

We are also considering ditching the Civic for something a little larger. The sad thing is that we bought it new in June 2011 (it's a 2012 model) and owe very little money on it, but we'd definitely be losing if we traded. So it goes with cars, though. The reason we got that particular car is because (1) my husband wanted something a little sportier than the Civic sedan, and (2) our downtown Charleston office has a SUPER tight parking garage. However, he has found the car to be a pain to get into/out of, nevermind the car seat issues, plus we are getting rid of our downtown office soon, and our other office has a normal parking lot. My husband really wants a convertible, but I convinced him that even with the biggest convertible we would never be able to enjoy it as a convertible until the kids hit a certain age (even the most comfortable ones are very noisy/windy in the back seat - we've gone on a bunch of test drives where I make a point to ride in the back with the top down), which means he would be the only one enjoying it for a while. I said that what we should do is either keep the Civic or trade it in for something slightly larger, then when we have more money to play with, he can get a 2-seater fun convertible as a third car, which we can trade off driving when we are kid-free. He really wants an MG or something old and small, so I figured why not wait and go the whole hog? As for a new car, we love Hondas and Acuras (we used to have the RDX), so I suggested either the Honda CR-V or the Acura ILX, especially if we can get a lightly-used car. (I haven't been a fan of the Honda Accord since the 2008 redesign. Our 2005 Accord was awesome, though.)

/car tangent

Anyway, you have a good point that the infant seat might be a good solution until we can do a convertible seat facing front, assuming s/he does not exceed the height/weight limits before s/he reaches age 2.

I had a 2007 Civic Coupe. It was a great car, but it was a PITA to get in and out of especially in tight parking spots. I'm not a fan of the 2-door setup anymore. It was reliable and easy to drive though. I love my Hondas.

I have a Honda Pilot now though which is enormous compared to the Civic.

Something like a CR-V could work if you guys are looking to upgrade. They are easy to park and not huge like the Pilot, but the hatchback is really useful for kid stuff. I really wanted one when I upgraded from the Civic, but oddly enough, a used Pilot was less costly than the used CR-V. I really love my Pilot though. We use it a lot for off-road and camping trips, and it's fantastic.

I never buy my cars brand new anymore. The depreciation is just money down the drain. I always buy them at least 2 years old. You end up saving 20-30% by doing that, and they hold their value a lot longer too.

You could also sell your Civic privately and get more money than you would on a trade-in.

Oh, I never thought about selling it privately - thanks for the thought! My husband and I work together, so depending on our court schedule we could possibly swing a few days with only one car until we bought another once we made sure the private sale was complete. At worst we could rent a small car for a few days.

I have never been a fan of coupes due to the doors. However, I much prefer its look on the Civic to the sedan, so I don't blame him for preferring it. I warned him about the difficulty with the car seat, but he really wanted the car. I think he learned his lesson. I forgot to mention that to fit his car in our garage, it can't be much bigger (wider/longer) than the Civic. We just totally reorganized our garage to allow him to park in there and to allow me access to both sides of my car. I'd hate to see him get something that would preclude parking in the garage. The CR-V or the ILX would both likely work. I'd have to look up body measurements on the latter, but the former would work for sure.

I drive a 2011 Odyssey, so we have plenty of space in that. As such, our second car does not need to be very big. My MIL has the new CR-V, and it's pretty neat. It's pretty maneuverable and fun to drive. I've always been a fan of that car (the Acura RDX we had is basically the same car). I like the Pilot, too, but it's too big for our needs. It is surprising how the pricing works, though, that you could get a better deal on a used Pilot than a used CR-V.

In the past we learned that used is the way to go, so we try to find a 1- or 2-year-old low-mileage car if we can. I think that's what we'll end up doing if we end up getting something else. They just make it hard to resist when new car financing is 0.9% vs. 4.9% or higher on a used car, making the payments rather similar if you're getting a newer, used car.