Can't tell you much about quad-core, as I moved to an AMD based setup since then and the 73pvm is collecting dust for now, but I think some of the problem reside in the 630i chipset, I'd go for anything with a slightly older chipset.
I can't tell you off the top of my head right now, but check the wiki for an Abit AN-M2HD. It's AMD based but the integrated components work really well and I think you can find an Intel equivalent pretty easy.
If you really insist on using the gigabyte mobo, the rout to go would be to disable the on board nic and just put a PCI nic in (or two if you want it as a core/hybrid) and just install the latest Alsa and Nvidia drivers as I described in the wiki.
Hope this helps