I'm not 100% sure of what you want. I have 3 tvs. I have 2 360's, a ps3, 2 ps2, and a an xbox going to them. I can tell you my set up and see if that helps.
46" lcd :
360 via hdmi, sound to amp via optical
ps3 via hdmi , sound via optical
hd dvr via hdmi, sound optical
amp visual out via svhs
pc connected via dvi, sound 1/8" to1/4" rca
360 via hdmi with sound to tv via hdmi.
ps2 via svhs, sound to amp via 1/8" to 1/4" rca
hd dvr via componenent/ sound rca
pc via vga.
co axl in for cable tv
composite for amp visual out. (I use my amp for svhs deck and a few other inputs)
27" crt sd tv (no component in) (eventually to be replaced with lcd):
ps2 via shs, sound rca
xbox via svhs, sound rca (modded xbox acts as media server)
co axl cable tv input
I also use my amp to switch other components like svhs deck, dvr, etc.
I love multi screen co op story mode gaming. Few pc games and few console games will have multi span for one game. Forza is one. But you need multiple 360's and multiple copies of the game. I like to play my friends in a non split screen environment. The hardest part is getting everyone sound. Headphones clear up the cluttered sound. The ps3 uses ps2 av connections, so it might be easier to have multiple cords and change them out. Or use your amp as a video switcher. I don't think having one image across 3 screens is possible without fancy video hardware. Or like street preacher said, the matrox is a triple out head. I don't think any games use it tho.
ps I would think about the 60 gb ps3 if backwards compatibility is important.