i run 6 newpac's on GS hub @650 Mhz (autotune, so some are bit lower) no problem at all. I think u are having a power problem, try a more heavier PS with at least 10A
you should run a R306 per port, dont stack em on a hub or you will get a bottleneck, but maybe when u use an GS hub you can stack
As far as i can see your MB should be ok, when running linux on it you should be even more ok
Limiting factors: as far as i know usb-port, but you got a lot of them, so that should be ok