The 9400GT, but a 9400GT is still crappy for gaming. I don't understand why you switched motherboards. Your Gigabyte board would have accepted the 955 just fine. You could have put the money you spent on the motherboard and RAM towards a new GPU.
thanks for answer megamanx00,
Your solution is better and cheaper but I have fear to update my BIOS on Gigabtyte because I never did that.