I saw that you said 6 750gb drives...

1TB NAS won't do you any good if you are looking to do 6 drives. If you are doing 6, you need them to all be connected to the same controller so you can RAID them together...

That macbook express sata card looks promising. There are quite a few 6 and 8 disk raid controllers and kits avail with esata out...
_________________________
"Fix it 'til it Breaks."

Jacob - EiC & Director of Technology
Mac Pro Quad 2.66 - 4GB RAM
160 GB SATA RAID 1 - 650 GB Storage
Quad 19" Widescreen LCDs
Accessorized to the Hilt