Hello, I'm looking to upgrade my graphics card from an nVidia Geforce gts 250 to a Radeon card; I'm working on a mid-range budget (150-250). I was wondering if the Radeon HD 6850 or 6870 would be a substantial upgrade? I've read that the 5800's and 5900's equivalents are better, but they are outside of my preferred price range.
So, simple clarification; with a 6870 I would see a significant increase in performance?
Yes you should see a reasonable increase in performance. Take a look at the THG Hierarchy Chart that shows a 3 step increase in performance. Note that THG does not recommend upgrading unless you get at least a 3 step increase.