By the way, I just updated a D915GAG system for a friend. It has two SATA III drives, and a nice new DVD RW, plus it is maxed out on memory.
The SATA III hard drives do not provide much, as the controller on the motherboard can only do SATA I speeds.
See section 1.7.3.2 on page 29 of this document: http://downloadmirror.intel.com/15197/eng/D915GAV_D915GAG_TechProdSpec.pdf
It is a nice board, for its age, and performs well enough. My friend finds it more difficult than me to let go of old hardware<G>.
Doc
