please HELP i don't know what to do . or what to buy
again...what is your budget? and why do you want to purchase 1337 card like 5770/4890? why n ot get yourself a gtx 560ti? or gtx 460se if you dont have that budget.
If those are your only two options for some reason the HD4890 is about 3 times faster than the HD5570. It also uses a large amount of power so make sure your power supply can handle the card.