careful, the Gigabyte board is non-ultra, meaning it has no SATA-II, activearmor firewall, overclocking options, hot swappable hard drives, and i believe the HTT speed is limited to 800MHz. Not really a good bet for high end. I'd either go for the A8N-SLI or try to find the Chaintech board somewhere else (mine's on order from newegg, but they're out, i think i saw some for $140 on ebay a while ago). Or, of course, wait a few weeks for the Asus A8N-E, the Gigabyte K8NXP-9, etc. to hit the market and occupy the $150 range. If you're buying a high end system, you'll be pretty pissed with the lack of functionality of the vanilla NF4 - in fact, it's basically a step down from cheaper NF3 mobos.
I had an A8N-SLI for a while, but the SATA-II controller died and i had to return it, so i can't give a great recommendation, but lots of people seem to love the board, for what it's worth. Things i liked: Fast, ran stable, every bell and whistle imaginable. Things i didn't like: SATA-II controller dying, confusing bios, long boot sequence, tech support hard to contact, couldn't tell if PCI lock was there/functioning, no bios option for NCQ.
I haven't received my VNF4/Ultra yet, but so far i've heard positive, and if you can find it for sub-$150, it's a steal. All the features the chaintech lacks compared to Asus are redundant - second LAN, second SATA controller, extra cables and adaptors, and a second PCIe x16 slot, so if you are likely like me and won't be using these things, then the 50% price savings more than makes up for these things.
Gigabyte's boards got great reviews for performance and features, but they are barely available, and not priced well (the Ultra board is currently $250, or A8N-SLI pricing). Additionally, the one that is available is the non-ultra, which is very crippled and priced in the Ultra range at $130+ shipping.