Just to clear up, the proc on these machines I am planning to purchase is a 2.4Ghz P4 (NOT celeron).
I do realize that VDPAU won't be release until MythTV .22 is released, and the drivers are still in BETA. I don't plan on compiling MythTV to reap the benefits of VDPAU, but I want to buy a card now with VDPAU support so that I am ready to take advantage of it when it's released (out-of-trunk) with Mythbuntu.
As for the debate about PCI bandwidth for VDPAU, according to the MythTV wiki there are several users who are using PCI cards w/ VDPAU, successfully. User Results
So with that out-of-the-way, with VDPAU enabled will I be able to play h.264 1080p video?
Also if I get one of these cards will I be able to play the HDHomeRun recordings (non h.264) on these rigs (w/out VDPAU)? Even without VDPAU the GPU should help with the playback of recordings, correct?