The answer to your main question is NO! The P55 Series motherboards do not properly support modern 3rd generation SATA 3 6Gb/s solid state drives. There were a few attempts to add SATA 3 6Gb/s support to a couple of motherboards. Results were mixed. [...]
Have they not had any success making any controllers/ mainboards that run well/ at or near rated speeds or does the lack of sata 3 performance lie in the nature of pp5 cpus themselves?
Cuz pcie sata controller cards come to mind and while i dismissed that idea after receiving your feedback on the Asus U3S6 Sata 3/ USB 3 expansion card I checked back to see if I could find a alternative that seemed more promising. Heres the newegg, some users report great success with this (http://www.newegg.com/Product/Product.aspx?Item=16-115-114).
I particularly found this review interesting because this is also on a 2009 board:
Installed on SATA II board ( Asus M4A78T-E ) with SATA III SSD ( Corsair Force GT 120GB ) attached and now gone from
223 Write 244 Read MB/s with onboard controller to
521 Write 542 Read MB/s With this card. Not The max but it's a GREAT!! improvement for this system.
Could this be the solution or am I missing something?