This subject is to do with three different Hard Drives; Western Digital Hard Drive 1002FAEX SATA 3 Hard Drive 7200 RPM Black Edition Hard Drive. If it would help; I am running Windows 7; Intel i5 / 760; 4 gigs of DDR 3 Ram and a hight end motherboard.
I may not have put this in the right context so please excuse me.
You ask about 3 HDDs, but only identify 1. What are the other two.
mgrzTX - If you are refering to the WD SATA 6 (not Sata 3) WD Drives, You are correct. The only Benefit that the WD gains with the Sata 6 interface is in Burst Mode - NOT worth wasting a SATA 6 Connection on, I have a WD 1 TB sata 6 Drive - MY BAD.
Some of the hybred drive that combine a SMALL SSD with the Mechanical drive may see a boost. You get the storage of a HDD and some gain in performance, This performance gain is going to be highly dependent on algorthim for "Quessing" what data you will be asking for. Myself, I'd go for seperate SSD and a Mechanical HDD. One of these days (years) the price of SSDs WILL come down.