The 4000 would certainly help you, but for the money I would look into picking up an Opteron. They overclock like crazy, supposedly have better silicon, and would cost you less scratch.
Example: my Opty 144. Cost me $144 (funny, huh?), I primed it last night for 14 hours at 2.88ghz. I'm working on getting it to 2.9 today. That's with 1mb L2 cache. That's higher than a stock FX57, for $144. And it wasn't really that hard to do, either.
According to the RTPE, you can pick up a 148 (which has the 11x multiplier) for about $255. Even a bad stepping of that proc should get you to 2.8 or better. Meanwhile, a 4000 costs $334. Hell, for that you could pick up an Opty 150. Or one of the lower-clocked dual core Opty's.
Just my take on it.