It isn't actually speed I'm after with this upgrade, I need more space, I'm down to about 12% in C drive and 8% in D drive.
Unless you have a reason or specific desire to keep it all in one box, you might consider external drives. USB-only ones are the most popular. But many stores (at least here in the US) have one or more triple-interface (USB, Firewire, eSATA) models. I have 9 of these in my setup.
