I don't know the circumstances, but are you stuck on that platform? There's not too many that would go for that processor. If you're an AMD fan, there better way to spend your money. If you're open to Intel, the 2500K is probably the sweet spot of price/performance now, but if your budget it tight and you're an AMD fan, then the Phenom IIs are a cheap way to get performance on a par (or better) with Bulldozer - the llano chips are probably better value as well - or for intel might consider the i3-2100?
I know you didn't ask about GPUs, but did you already buy the 550s?
The 2011 PC Market in Review; Hits and Misses
If not, you want to go with a better sinlge card solution (6950 maybe).
edit: this is a good budget CPU if you want to buy AMD:
AMD Phenom II X4 955 Black Edition Quad Core Processor 3.2GHZ AM3 8MB Cache 125W Retail Box - AMD - HDZ955FBGMBOX