I don’t know that the Velocirapters actually perform as claimed. There might be some Windows/ Buss driver issue, but Windows defaults my Velociraptors as Multi-Word DMA 2 devices! 
Do some research on Velocirapors and actual throughput to see for yourself…you might find the Caviar Black series is actually more bang for the buck!
Can’t answer for the Gigabyte offerings… After I had a Gigabyte P4 offering (GA-8KNXP) just stop working two months before the warranty expiration, having it repaired under warranty only to have it die again one month after the warranty expired, I decided to try a new manufacturer. I’m not saying Asus is better or worse than Gigabyte…just that it’s very difficult to get the whole picture unless you have tried it for yourself! A great place to start researching is on the manufacturers forums to get a glimpse of the types of issues others are having with a particular offering!
I know you know this already, but when it comes to computers… there are just too many variables to be overly decisive! But as I’ve said… I’m really happy with my present machine! 
Al