for a gaming cpu, and inside AMD, the Phenom IIx4 is the best chip out there. if this is soley for gaming, i would recommend either a 955BE for easy OC, or something higher in the series if you dont want to OC. the new FX series out, aka BD, dont really provide good enough benches to provide any reason to stray from a trusted and tested cpu in my mind.
Best of luck.
P.S. the 955BE is in my system, OC'd to 4.12GHz on air cooling. I bought it for $115.
if you dont mind running a micro mobo, you can find a 890, and possibley a 990 series if you shop and get a deal you can easily get a great board. check and see what is out there, im guessing 70e is appr. $85??? not too updated on the exchange rates. Point being, you have a sufficient amount of money budgeted to get a very good board. What purpose is your computer for? Primarily gaming? What type of storage will you be using? Do you do any application/media based projects?
The FX-4100 might turn out to be a very good CPU for the price. Wait for some reviews to show up. It basically costs about the same as the Phenom II 955. And be sure to buy a 990FX mobo, so you can use the next series of AMD CPU's.
unless you are going with the new Win8 coming out, since supposedly there are supposed to be wonderful software enhancements, its not smart to spend $120 bare minimum on a 990FX board and a $140 processor JUST FOR GAMING. Im sorry, but the FX series is incredibly based off of application use and Servers...not gaming desktops. While the 4100 series MIGHT be a good chip, we just dont know. and benches will take at least a good 2 weeks just for basic variety. It will take a good month before we get a good bench table straight across the board.
for $200 (roughly 160e as a rough appr.), you can get everything for a well known, heavily benched processor and mobo combination. If you want to take the plunge andy, go ahead, but im a firm stickler for proven hardware.
If you want a better processor, go with an i5, as it will blow any FX chip away for gaming. and its only $220. You can start doing your own exchange rates as i think im really not educated enough to continue posting them for fear of retribution and mocking...