My current system: HPE-510y. The only upgrade I've made to date is the addition of a Crucial M4 128GB drive, which I use both to hold WoW and D3, and to act as the boot drive; the OEM drive houses the 'non-essentials.'
I'm hoping I can realize a significant improvement in video performance both for WoW (both current and MoP (on release)) as well as Diablo III with an investment of under $200 towards a better video card (and, if as I suspect will be required to support it, a power supply) than the AMD Radeon HD 6570 1GB card included in my system. Obviously I'd like to be able to run at the highest settings and resolution possible, whereas right now I'm running on the "Good" settings and managing 20-30FPS in 25 man raid combat at reduced resolution (1440x900). Solo, or 'around town,' I get 50-60FPS. I currently run WoW in windowed mode, and am using a single monitor.
I'd love some input on what would be the best compatible upgrade (card or card+power supply) to fit my machine and budget, with a 'napkin math' estimate of the settings level / FPS I'd likely be able to set / achieve -- or if I wouldn't see any reasonable improvement without spending more.
Original PSU is just 300W, which can't support fast GPU. It's barely enough for current setup. So you need new psu too. Expect to put $/€/£ 50-60 for psu and rest for GPU.
For GPU choice, in the general price range: GTX 560, HD 6870, HD 7770. Former two are bit faster and bit more expensive. The latter is a bit cheaper. HD 6850 is also a possibility, if you can find one cheaper than HD 7770.
Would you care to specify where you and thus which retailers you have available in your country?