I tried the latest VoodooHDA again, and, besides being more difficult to install, the sound quality was worse than that with the VMsvga2 driver, which thus still seems to be the recommended one for Snow Leopard Server VMs.
BTW, from what I have read on the web on different forums, the built-in AppleHDA driver doesn't work in Snow Leopard Server because on that OS it only supprts a limited range of devices; while in Lion and Mountain Lion it also supports the VMware emulated sound card natively: that's the reason why one must use AC97 (es1371) audio in Snow Leopard Server.
Just FYI...