Congrats on the new home!
I would keep the Denon, since you say it is fairly new; I'll check the specs after work. Sell the Yamahas and the Polk subwoofer. No disrespect to Polk as they make great speakers, but a quality SVS would blow that sub out of the water. ( plus your room is quite big meaning a Powerful sub is needed. )
For speakers, there's a thousand options...
From my experience I'd go with the Paradigm Monitor or even the Reference speaker line. ( whichever fits your budget best ) And there is no necessity to buy a pair of towers, as opposed to bookshelves. If you go with a potent sub, the extra drivers present in the towers would not be needed as much.
If you plan on going with an SVS subwoofer it would be a good decision, great bang for your buck sub, like other online speaker/sub companies. I'm sure you will be given many options, but my advice is from personal experience.
Enjoy my friend!!
update- below is an example of what I was referring to originally:
Main Speakers: Paradigm Mini Monitor $600
Center: Paradigm Center 3 $600
Surrounds: Paradigm Atom Monitor $400
Subwoofer: SVS PB-2000 $800
Total ( retail prices ) $2400
Last edited by Deckard97; 06-22-2014 at 03:41 PM.