no ati cards currently work well enough- they all have the same texture upload problem in 10.6.4/5
4870- 5770 5870-
its not fixed in todays 10.6.5 release.
gt120 is simply not good enough to run more than a couple of low res outputs- it overloads easily with triple heads.
gtx 285 as the best option for most of this year.
quicktime video digitisers dont work in 64 bit mode - apple never ported the API to 64 bit - IE any decklink or aja model-
everything needs to run in 32 bit modes.