What resolution do you play at? 2 4770s will perform similarly to a 4890, so it depends on your budget, if you have a decently high budget and can fit in a 5850 that would perform significantly better, if you only have a $150ish budget a second 4770 is your best option, just make sure you have the PSU to support it, a decent 650W should suffice.
Wow that was fast
I have been testing out different resolutions so I don't quite have a distinct one yet :P. My monitor can support 1920x1080 so probably that. Yeah $150-ish is what I was looking at. I have a 700W so I should be covered I guess. Thank you for your answer I'll go for the second 4770. Best Answer :P