I have the XR55 and a PS3, and it's a pretty good combo, but it would be better to have the XR57. Did you just buy the XR55? Or have you had it for awhile? The thing about the XR55, is that the sound is absolutely amazing, but it doesn't have HDMI, so that means no lossless sound. Ideally, Panasonic would come out with a brand new model, similar to the XR55, that has HDMI 1.3, and can layer DPLIIx on top of 5.1 and 6.1 LPCM, and can do the full 7.1 LPCM, and doesn't have any bass management issues over HDMI. Unfortunately, I don't see any on the horizon that fill all those requirements.
The XR57 can do lossless 5.1, but it can't do lossless 6.1 or 7.1, and it can't layer Dolby Pro Logic IIx over lossless 5.1. It also has the bass management issues.
Having said all of that, my XR55 still sounds amazing with Dolby Digital 5.1 and DTS 5.1 with DPLIIx on top making it 7.1, but I do wish I could hear the true lossless sound. I'm planning on upgrading soon, but waiting to see if the Onkyo 605 does everything I need it to. The jury is still out on that.