Bigger is always better.... if you think you have enough, for a home theater, you will always wish you went bigger....
PB12-NSD, 20-39 PCi
I bought a Plus/2 and then I added a Plus... worked so nice in my huge room, but I ended up getting hooked on the subwoofer bug, and bought some 15" drivers and Im going to make my own subs, and see how much better DIY (do it yourself) will be...
Go just a touch bigger then you are thinking about, and you be less likely to want to upgrade... Just one mans opinion...