Ok so (luckily) I was able to get a Mac Radeon 9800 with 256MB (R350 0x4e48) and swapped it with the 9600 XT. However things are not much better. Although I have modes > 1080p available in "Monitors", they do not show up on "Screens" - max resolution that shows up there is 1680x1050 (while with the 9600 XT I could at least use 1080p). I can edit (and test) modes > 1080p now (so the bug I had before is gone with this card), but I can't use them. Am I missing something obvious here?

Thanks