Heart Rate Monitor For Fitness & Running?

Hello all of you wondering MFP people!

I need your help! Please? ((bats eyelashes))

I recently came into some birthday money (woo!) and am putting it to a new heart rate monitor watch. I need something that will track calories burned and heart rate during exercise, but i also need something with additional tweaks for runners (I'm not a pro by any means but it is an activity I love and do very often during the outdoor season here) .. interval timers etc.

I'm looking at the Polar RS300X and the RS400 right now. I had been eyeballing the rather cheaper Polar FT7 but it doesn't really have any of the runner-specific features I'd like so I'm leaning heavily towards one of the RS models.

The only heart rate monitor watch I've owned was a Mio watch, and while I loved the interval timing/countdown features, i really hated the only-worked-sometimes two button heart rate sensor that ONLY gave you readings when you pressed those buttons, and didn't always work.

So.. I'm not set on any particular brand or model and can definitely be sold on alternatives, the Polar models are simply the ones I've been leaning towards,

help please?