For gaming, you don't need 8 gigs. But me telling you isn't any better than anyone else telling you. So do this, fire up EQ2, load up a system demanding location, then go into task manager. See how much physical memory its using. But unless you're running 4 apps in the background while gaming, the OS will use 1gb (vista, a lot less for XP or Win7) leaving 3gbs for apps. Fallout 3 uses less than 1gb when I've looked and GTAIV, as unoptimized as it is, only uses 1.5gbs. Thats still a lot of leftover room for other background task, even if EQ2 is on the high end.
Cas will be listed as CL in the model numbers sometimes. Lower is better. 9 isn't terrible, but for the same money, you can do better. And that's what the point of this is, right?
Saving some more, if you're only doing 1 GPU, then you will be fine with the gigabyte ud2. Unless theres a specific feature the ud4r offers, the boards will perform similarly.
You can also cut down on the PSU and get just a 550w from a good name.