When I posted this question it had to do with the under performance of our very expensive workstations (Dell Precision 670) and how perhaps getting an $9K 690 with a total of 8 cores could help or not help with the situation. I had contacted SAS about this issue a few years ago and the only solution they gave me were the sortsize, bufno and SGIO. That marginally helped with the problem.
The real problem was with hardware which took a random SAN engg. who is totally unfamiliar with SAS to figure out. It as as simple as enabling "read cache" on the RAID controller card.
I wish the help desk person had told us about the SAS performance consulting service (we certainly have the resources for that) rather than saying "Well if you have 4 x 10K RPM SCSI drives in RAID 5 and dual-dual cores and 4GB RAM and sortsize=2g, I guess thats as fast as your processes will ever be."
All it took was a H/W guy to tell us what the problem was........after two years of thinking this is the best it could be, coz SAS said so.