90% reads, 10% writes...

Reading a couple of chapters from the link you posted pretty much narrows things down to a RAID5 or 10 (which is pretty much were I got to before posted this thread), I guess my main concern now is, would the 10% write ratio really degrade the read performance of the RAID altogether due to the parity necessity?

I had a RAID 5, spanning across 12 spindles, that would give me over 6TB and 11 usable spindles, correct? I'd probably move my Data and Index files to this storage array, placing my log files and tempdb on the other RAID 10 array.