Re: Best nvidia card for video playback on Linux?
6800 no letters AGP or 6800GT/Ultra AGP or PCIe.
6800 PCIe and all 6600 variants and 7xx0 remove some hardware capability for playing video with the 2D engine which has Linux support. On these cards some video capabilities have been transferred to Purevideo which is using the 3D engine and is not supported by Linux (not to mention I wouldn't like to fire up the power-hungry 3D engine needlessly).
I run my 1920x1200 display with a 5900XT which is about perfect.