Technically your great room is much larger it's because there is no door to seal it off from the other areas so your speakers will "see" the rest of the space. Not a big deal for your fronts or surrounds but it is a big deal for your subs. If you want really good bass your going,to have to have a lot more sub than 2 12" subs. If killer bass isn't a big deal to you then you"ll be just fine with what you're getting.
As far as your surrounds go, 80 Hz is fine because it is the THX spec for crossing over to your sub. Cone marterial doesn't matter. The paper vs Kevlar vs polypropylene is all BS. A good speaker is a good speaker. What matters is how well it's designed, not the cone material. Angled woofer, doesn't matter, angled tweeter, yes. $300 I think is a bit over kill. Not a whole lot of sound comes out of the surrounds so they're not nearly as critical as your fronts. 100 watts power handling is more than enough and I would go with the same impedance as your fronts which I believe are 8 ohm.
Television: Mitsubishi WD65737 DLP
Processor: Emotiva UMC-200
Amps: Carver AV 806x/Behringer EP4000
Mains: DCM TimeFrame 600 Center: AT 453C
Surrounds: AT 251.1 Sub: Danley DTS-10
Blu Ray: Panasonic DMP-BD655