A used or refurbished 58xx card for only a little bit more will get you allot higher hash rates. They sell broken ones even for 30-50 dollars sometimes and they hold their value more than any other cards. A 5770 = a 6770 I think, there ok but the 58xx ones are cheap beasts.
I'm not bias towards amd or Intel or anything, Intel seems a little better for low dollar cpu's lately. I think this is a deal that wont be around for long that I'm about to post, you can use PCI extenders if you end up getting more cards but it has one GPU slot.