2 months ago I made a mistake - bought an a10-5800k apu. I really wasn't gaming at all, so I thought a dedicated gpu would just be a waste of money. However, recently I have started gaming again, so I thought that maybe I should add a dedicated gpu to my setup. I just want smooth 1080p experience (I am fine with mid-high settings, but ultra, of course, is better). So, which gpu would you reccomend me? I am looking at hd7870, but won't the a10 bottleneck it heavely? I have a shitty (3+1 phase, no vrm cooling) motherboard, so overlocking the cpu is a no go. I also have a 430w psu (corsair cx430). So I am not sure it will be able to power a hd7870. I know I could add a hd6670 and hybrid crossfire it with the integrated gpu, but I think a dedicated gpu would be better.
I have a 660ti and a 4.2 ghz 3570k on a 450w power supply and it's running great. If your psu is decent then it's should be nothing to worry about, especially since you're not going to OC your cpu.
Here's the 7870 pulling 284w on a 2500k system. http://www.legitreviews.com/article/1967/11/
Tests of the 5800k shows it drawing a bit more power than the 2500k but as long as you've not connected 100 drives and usb devices you should be fine.
The better gpu you buy the better performance you get in most games. There will be games that you'll be cpu limited in, but they'll be in the minority.