I hate to watch my family go use the friend's pool because ours is too cold!

I could use some help picking the right heater. My pool surface area is about 500 sq. ft. with a volume of about 1900 cu. ft. (on-ground 24' round) and I live in RI so I'll want to raise the temp 20-25 deg. F. I have Natural Gas at the house and do not want to deal with Propane tanks.

I'm looking for something reliable (fewer fancy features a plus), efficient, and fairly quiet (in that order).

I'd be thankful for your suggestions and experience!