I'll put my vote in for WAR.
7.1 PCM audio from the PS3 into my Denon 2808 and the neighbours were worried
Dont get too hung up on 7.1 tho' as most standard 5.1 / 6.1 soundtracks can be great too. Take the start of Ratatoulle (5.1 PCM on BD) as an example. On my system the sound of the rain as the camera pans onto the farmhouse is so realistic its as if you have been caught in a downpour for real.
Also good for a test (laugh) of surround sound is Die Hard 4.0. The apartment shootout / explosion at a high volume is a sure fire way to get an ASBO