For the subwoofer check out the Rythmik FV15 and Epik Legend. I don't know that they'll be able to pressurize a 4000 cu. ft. room, though; you might have to up the budget to achieve that.
Canton and Polk make some nice speakers, but telling you which will sound better is virtually impossible for a couple main reasons.
1) We don't know your preferences
2) We cannot listen in your room using your gear
Preference/bias always plays a role, and the room acoustics can effect the sound you'll hear more than the speakers. The best way to determine which to purchase are to audition and study measurements, then bring the final candidates home for a shoot-out.
With that said, if you purchase the Polk's can they be returned within 30 days if they are not superior to the Cantons?
P.S. I bet if I google "Home Audio + Miami, FL" I find at least two good AV stores for you to audition at. In fact, I already did (Cartronics and Sound Components).