I was currently about to purchase a i5 2400 cpu, but noticed Newegg had a $15 promo on the FX 8120 .
189 for the i5 2400
159 for the 8120
139 for the 4170
The system was originally to be paired with a 6870, but with the savings from the CPU I could go ahead and get the 7850.... Power should not be too much of an issue since I will be trading CPU to GPU power consumption. But for primarily gaming what would be the better option? an AMD with a 7850 or the 2400 with the 6870?
.... well I just sucked it up, went the direction of the i5 3450 (have no real intention to OC) Its 199 but I will suck it up, run off the "HD2500" for a moth and "splurge" on the 7850. Compromised on my last system and kept updating it, might as well bite the bullet on the new one. Seems the AMD is only good if you want to OC the thing.
What Motherboard? Because those cpu's are different sockets, You can find good deals on 1155 socket motherboards some are gen3 get an i5 2500 or better 2500k and get a 6870 then upgrade to crossfire or upgrade to an IB later if you want or even still get your 7850.
I don't know what your price limit is here or what you really want out of it.
But if you have a very limited budget and don't plan on upgrading much go with the 8120 and 7850.