Yep, I have a setup shown in my sig and I just grabbed an X2 4800+ as an upgrade for Xmas... probably give me another year or two of life before I do a system build again...
The 4800+ can be had at Newegg for $248; they also have the FX-60 for $448, which is the fastest S939 chip out there. In both cases that's the best price around. For me, the 4800+ made sense because it's $200 cheaper; the extra money for 200 MHz and an unlocked multiplier wasn't worth it.
But those are the two best chips on 939 and they WILL be completely off the market by New Years; get it now if you're going to.