For wire, you might want to go for some 12ga Belden wire from
Westlake. They have awesome prices, and the wire is rated for in-wall installation. Even with shipping, it'll best just about any other price. And you don't have to drive for it!
As far as speakers go, are you basically limited to online ordering only? If so, have you considered options from
Axiom and
AV123? AV123 makes especially pretty speakers (that sound good too, of course) which should help you justify the price to the wife
While they don't make in-wall speakers, they still make good quality stuff for awesome prices, and both places offer long return periods so you can check out the speakers in your home. The out-of-wall offerings are still a good option though, as you can tweak the placement of the speakers more to get the sound you desire.
As far as subwoofers go, yes subs are needed for movie sound effects, but subs are also needed for music. It helps fill in the bottom end where most speakers just can't tread. Going for a good sub will make your music and movie experience way better. Since you have a big room, I think you should look at the offerings from
SVS. Their big cylinder subs and their larger box subs will rock you. Hard. And still, they have the ability to do music too, not just huge explosions. Besides, many recievers offer you the ability to disable the sub and just listen to music through your front two speakers without any extra processing.
If you wanted to really go all out, an in-wall system from
RBH would kick major arse. They are used in many reference systems here at Audioholics. They're expensive as heck, but they'd pump out the sound. Probably out of your price range though.
Do you think you'll need HDMI or DVI switching? If not, you might consider the option of a Yamaha RX-V2500 receiver and an Emotiva amp. Lots of options...