Okini, you are a ******* retarded piece of trash. Honestly i have no hated anyone on a forum as much as you in all my life. you are constantly giving out bad advice to people, in the form of one sentence, that gives nothing to back it up. And every time you have tried to back up anything you have said you were shot down by everyone else. Or you just copy someone elses message and post it as yours. Please for the love of god if you are going to give advice at least research first. And then you have the BALL to go around asking for advice when you have been telling what other people to buy like when you made your newest "Which PSU" thread!!
Anyways at the OP. The 5830 is within a few fps of the 4890 in almost every single benchmark. And with AA/AF/High resolutions tends to get better FPS. But for the price premium it has over the 4890, the 4890 is a better buy depending on what games you are playing.
And As pretty much everyone has stated, a 5770 will handle your graphics just fine.