Not sure what you mean by without E8400. That CPU is supported with a BIOS update, however it will be nearly impossible to find one new.
I wouldn't spend a lot of money on this build the rest of the system will seriously handicap any decent video card. And then there is power to worry about. What kind of power supply do you have?
Not sure there is a 256bit 1GB card in existence. Anything that I would put in this build has a 128bit bus or smaller.
GTX750Ti would be overkill, but uses very little power so should be a safe choice.
Something like a GT640 or R240 would probably be about right.