Keep your eyes open on the reviews and shootouts between the AE900 and the Sanyo Z4. Currently, the only head-to-head I've read indicates that the Z4 may be a slightly superior overall machine for the money - and it saves you a couple hundred bucks.
But it from VisualApex - you will NOT be disappointed with them!
If you are making a screen, but can test the projection/screen size before building your screen, then I would recommend that so you actually end up with a screen size that you are really happy with. Some prefer going a bit smaller for the extra brightness, others like bigger for the 'Wow!' effect.
Double check: Don't the Def-Techs all need power outlets right next to them as well? Do NOT forget power! I would download the manual to double check on whether RCAs are needed at each location for their sub. It may just pull that signal off the speaker level input.
I'm personally not a fan of Integra. Just my opinion though. I don't think their engineers are as good as the guys at Denon, Yamaha, or Pioneer.
Monster CI/PRO 14/4. Search Monster 14/4 on eBay and you will can pick up 500 feet for about 150 bucks. Yes, CL3 rated for inwall use. Very, VERY! flexible stuff with wiring that strips well and works excellent. Until I find anything better, that is what I recommend to everyone. I don't recommend almost anything else from Monster and I do recommend eBay for your purchase. You can sell what's left over if you need to. But, better to have to much cable than to little.
I would definitely run wiring to allow for bi-amping down the road. 14/4 will give you that option.
Don't forget the RCA AND power connection for the subwoofer location.
Run conduit to the projector! You also want to consider the power requirements for the room and ground loops which may be introduced into the system - especially the projector - by electrical circuits being on different loads. I personally ran all my equipment back to a single location and a dedicated 20amp circuit to run it all. Everything BUT my projector. The projector has some interference. The plasma, which is run back and runs off the same equipment, does not have interference. So, I will run power from the projector to the central location now as well.
How? Conduit!
Make sure to run 1 HDMI cable to the projector, plus at least one component cable (3 wires) and 1 composite cable (1 wire). I would also throw a piece of CAT-5 in there as well.
If possible, I would avoid putting the A/V equipment at the front of the room under the screen. Blinking lights and such can detract from the film watching going on.
Have fun with it!