Asus, DFI, MSI..each has a few socket 939 boards that are all within .5% of each other in various benchmarks....
(I use an MSI K8N Neo-4 that is flawless at stock freqs, but the mb doesnt seem to like any FSB above about 216 Mz, despite a new BIOS flash, lower HTT, more core voltage, lower mem ratio, etc...; the Asus and DFI models are both well respected, and each has a god rep for stability and overclockability.....)