Don't hold your breath for XVMC on nvidia 8500, 8600, or 8800
I emailed back to Ken Spencer at nvidia, asking if the lack of XVMC was due to hardware differences on the 8x00 series, and got a "Yes" answer back. Nvidia says they have no plans to provide XVMC on any of these cards:
I am glad to hear that your 8500GT is working well for you with the
exception of XVMC support in Linux. This is a hardware limitation that
involves all 8000 series graphics cards. There are no definite plans at
this time to provide XVMC support for the 8000 series graphics cards.
Make sure you have a powerful processor if you want to view Hi-Def content with one of these cards under Linux. As I stated earlier, the Pentium D 805 seems to pretty much work for HDTV (I use a seperate backend for mythtv).