I'm about to upgrade a computer but to keep costs down want to re-use as much of the old one as possible. I have an HD 6670 so was thinking about going for the AMD A10-5800K plus A75 motheroard. But, the powersupply is only a 350A unit. Question is would an I3 plus a graphics card to match the dual graphics take more power or less and would I see any real performance diffference either way.... don't want to have to spend 200$ to get better graphics either - I do like gaming and mostly word and excel plus internet works .
Get the A10 5800k or 5700 if you don't overclock and possibly a A85 Extreme 6 from Asrock, invest in faster RAM too DDR3 2133 is about optimal for an APU. Powerwise it is probably wise o invest in something sturdier than a unknown 350w unit the status quo in most tests is a Corsair CX500 which is a solid lower cost unit.
A10 vs i3 is generally close in performance the i3 may in instances who a lead but its not really worth it when you consider the platforms, the A10+A85 gives you features seen on the higher end Z77 platforms which you are not going to stick a $130 part onto a $200+ motherboard.
Go for the A10 if you are going to overclock immediately or eventually. The means you need to buy a another heatsink though.
I believe the HD 6670 Crossfired with the integrated HD 7660D would be about (no quite, but about) equivalent to a HD 7750. However, I'm not sure if the Trinity iGPU will work with any of the upcoming Radeon HD 8xxx graphic cards.
There is more longevity for AMD's socket FM2 than there is for Intel's Ivy Bridge socket 1155. AMD will be releasing a tweaked version of Trinity called Richland probably by mid 2013 and is confirmed to be a socket FM2 APU. Intel's socket 1155 is approaching EOL (end of life)... or you can say it is now basically dead... Intel's next generation Core i3/i5/i7 CPUs (Haswell) coming out this summer will be socket 1150 and not compatible with socket 1155 motherboards.
The longevity of AMD's socket FM2 is uncertain though. Kaveri is AMD's next generation APU based on the next gen Steamroller CPU core. Steamroller is a totally different architecture than Piledriver (used in Trinity APUs), and it is too soon to know if it will be a socket FM2 APU. Steamroller is not expected to be released until 2014 and there have been rumors that Kaveri has been cancelled. Yet there are other rumors stating Kaveri is not cancelled.