I haven't done any reasearch at the moment, but is there any sense to change my GPU for a newer one now, for example HD 6850? 4890 runs all the games quite smoothly, but a bit bigger and smoother fps wouldn't be bad . My 4890 is really noisy, even at 50% and runs extremely hot >100c (good airflow and three fans in my case) and has DirectX 10.
I could still get quite a good money from my 4890, but is there any sense? If there is, I would like to have a"bang for buck", future proof and not noisy GPU. And would there be any bottleneck(s) in my system?!
The HD6850 wouldn't be much of an upgrade in terms of performance(+20% vs a reference speed HD4890.) You'll have to spend more for something along the lines of an HD6950($300) for a truly worthwhile upgrade. That card can also unlock into an HD6970 so it is a nice deal for the money if you can afford it.
get a 6870 now, it will give you about 40% better performance then yours now, then get another next year when the new video cards come out because the 6870 will probrably drop to about 150$, and 2 6870's=30% better then a 580gtx
Benchmarks I've seen have the two close. Currently, only the 6000 series as morphological AA, so I'd go that route. It's not something you'll use all the time, but it's great when the game has no other AA option.
The 5000 series also had more technical problems, such as the vertical bar crash. It's possible that's been resolved with the non reference designs, but I'd rather not take the chance.