Supposed to be cheaper than a 4890, I'll believe it when I see it.
Dates have been pushed back to the 5/2 by the looks of things, which is a shame (but I can wait, I've waited this long).
I'd personally say hold on for a little while longer, see what price the 5830 is, if it's in price range then it's a winner, if not then going for a 5770 is probably going to be the option for you, you'll see an improvement even, seeing as you'll be going from 512mb to 1024mb
I'm also going to go against the grain here and suggest a 5750, it's not quite as powerful as a 4870 1024mb, not sure how it compares to a 4870 512mb, however the real bonus comes in crossfire, these cards are already relatively cheap, when they drop in price a bit more grab yourself a second and you'll have a relatively cheap and powerful setup.
Dates have been pushed back to the 5/2 by the looks of things, which is a shame (but I can wait, I've waited this long).
I'd personally say hold on for a little while longer, see what price the 5830 is, if it's in price range then it's a winner, if not then going for a 5770 is probably going to be the option for you, you'll see an improvement even, seeing as you'll be going from 512mb to 1024mb

I'm also going to go against the grain here and suggest a 5750, it's not quite as powerful as a 4870 1024mb, not sure how it compares to a 4870 512mb, however the real bonus comes in crossfire, these cards are already relatively cheap, when they drop in price a bit more grab yourself a second and you'll have a relatively cheap and powerful setup.