The FX-9590 was nothing more than a factory-overclocked Vishera, so clock-for-clock Steamroller will beat it out no matter what. We currently don't know how the desktop Kaveri will clock, but if it can somehow clock as well as Richland could, it would put up some damned good performance... I don't think the single-thread perf will reach Sandy Bridge levels yet, but it should come close to it. I'm thinking at least Nehalem or better.
I think it will replace the A10-6800k (USD $150) as the flagship APU so it'll probably be $150...In which case if the CPU perf is great and the iGPU really is on par with the HD 7790, this chip will be flying off shelves (real ones and virtual ones.) I don't think the iGPU will be that great though. Realistically it would probably be around 7750 DDR3 or 7770. I don't expect huge strides in performance increases, though that's just my realistic/slightly-pessimistic outlook there.
Edited by NaroonGTX - 9/21/13 at 5:51pm