I'd strongly recommend skipping the surrounds. I have 3.1 in my projector-based HT -- M3Ti L/R, VP100 C, TN-1220HO sub -- and I'm very happy with it. It'll save you the cost of 2 speakers, and all the wiring, mounting and receiver setup associated with the surrounds. With a center, you get control of dialog volume, and pin dialog to the screen, and for most movies the surround effects aren't important. With 3.1 you get a lot of sound information already.
Heck, if they're not fussy about bass, you could get 3 M3Tis (which has nice bass extension for a small speaker), skip the sub, and have a pretty darn good HT system. That would give good control of dialog volume, not compromise sound quality for anything but true bass, be very simple, and be cat friendly. Subs are always floor mounted after all.
Not to change the topic, but my TN-1220HO looks amazingly like a scratching post.
--Martin
