what i don't get is why you have a hd 5770 with an a8 instead of using the integrated 6550d graphics, the apu will bottleneck the 660ti the a8 3850 is meant to be hybrid crossfire with a hd 6570 http://www.amd.com/us/products/technologies/dual-graphi... im not sure does your motherboard support hybrid crossfire though
With your current hardware, there is not much more you can do to improve performance -- I wouldn't suggest buying a HD 6570 or a 6670 as recommenced by AMD, even if it were a fraction of the price.
Your Mobo is an FM1 socket, and they only support A-Series and Athlons. You'll need a new board and a CPU if you don't want to bottleneck that GTX 660 Ti you have your eye on. Installing the GTX 660 on your current configuration would feel very wrong, despite the improved performance. I would keep your HD 5570 CrossFired with your integrated GPU until you're ready to replace your board and CPU.
the 6670 is for a different apu not the one he has, his a8 3850 is compatible with a 6570 he doesn't have a 5770 crossfired with it his using that as a stand alone gpu, for 50 quid its the first thing I would do (if the motherboard supports hybrid crossfire) it will increase performance over the 5770 which you shouldn't have been using anyway as it is marginally better than the integrated graphics of the apu
AMD recommends the 6570 for the OP's system because it provides the highest performance over price differential. However, I erred when I assumed the OP had the 5770 CrossFired with the on-board 6550D GPU. In this case, an upgrade would definitely be in order in lieu of a significant overhaul.
Q2: How do I know my AMD Radeon™ HD Graphics card is capable of supporting AMD Radeon™ Dual Graphics?
A2: There are two main ways to find out if your system can support AMD Radeon™ Dual Graphics. One, you can go to www.amd.com/dualgraphics and get the latest information, including all supported discrete GPUs. Two, if you purchase an AMD A-Series APU for your desktop PC as an individual processor-in-a-box (PIB), the right hand panel will show the supported discrete GPUs for that particular APU model.
I can't say for sure about the A8 3*** series although according to AMD there is no support for the HD7000 but I know for a fact your link has wrong info for the A8 5600K