Thanks for the suggestions!
I had a feel of the 2nd hand 5D yesterday, but everyone in the shop was harping on why i'm getting a 2nd hand camera, and edging me to get a new 5DmkII (with the better color reproduction from the Digic IV sensor, great screen etc). Even when i mentioned i have a budget constraint, they suggested for me to get a 50D instead, as it is Digic IV compared to 5D's Digic II, as well as the screen, and confidence of owning a new set as compared to 2nd hand where you don't know the history of the camera. Everyone is kind of discouraging me from getting a 2nd hand 5D...
Is the difference in the Digic IV vs Digic IV sensor that great a consideration to offset the benefits of full frame?
Does the improvement of LCD screen for 5DmkII/50D over 5DmkI matter that much to you as a photographers? I guess it is to allow us to preview our shots and make necessary adjustments in settings?