EVGA 7800GTX 256mb
This card works hassle free with a 7.10rc 64bit DVD install on my Asus P6T deluxe/i7 920 core/hybrid setup, and netbooting Asus A8N32-sli-deluxe/FX-57 MD. (both require drives be set APCI mode set in bios, though I'm not sure if that has anything to do with the video card. -the screen goes black right after first install menu and doesn't come back when drives are set in sata/ide mode) In this setup the cards will handle 1080 HD content in UI2+ alpha with minimal tearing on core/hybrid, tearing is worse on MD but still watchable for all but a few 15Gb+ .mkv movies- those wouldn't even play correctly under windows with this machine. core/hybrid playback is nearly flawless.
GTX cards are not ideal for HTPC- they are too large for many htpc cases, power hungry, and hot- but it's what I had laying around.
Read about my setup/newbie experiences here: http://wiki.linuxmce.com/index.php/Asus_P6T_Deluxe_i7_920