get the 4890, the 5830 is over priced.
If you want DX 11, get the ATI 5770. The 5830 is not that big a step up from the 5770 and the 5770 is a solid jump from the 9800GT.
There's actually an HD5830 on newegg at the moment for $215($200 after rebate);http://www.newegg.com/Product/Product.aspx?Item=N82E16814102878
That price actually makes it a reasonable choice, especially if you OC the card. That said if your resolution is below 1920x1080 then I would say just get the HD5770.