There are quite a few 939 boards about. However, there are none about now that support PCI-Express I know of (if there are, please reply ). I'm just going to say one thing though, A8N-SLI. This board is a killer in pre-release reviews, SLI is storming again. The great thing about it is that you can grab one GFX card now, and one later, to keep costs down, and performance up.
Have a look here for some examples of difference between SLI and standard : http://www.behardware.com/articles/536/page6.html. DOOM3 at over 100fps, 1600*1200, 4x/8x is more impressive than anything else I've seen.