I have 4x4GB, 2x2GB, and 2x512MB sticks. Some are 533 and some are 800. There is no requirement for pairs, and you can put different sizes in the box in any order and any speeds. None of the chips are ECC. The cost versus benefit wasn't worth it(cost is quite high for 4GB sticks).

Spoiler - There is a set of benchmarks I did with a pci-e RAID card I had. Not sure if that helps you at all since you wanted onboard and discrete. The benchmarks I posted yesterday are from an onboard card, while the first set I did was using a software raid as well as pci-e card.

Does anyone else notice that when you post messages it says it got posted, then it shows you the thread with the new message. Yet when you go and check later the thread is missing the post? I've had this happen at least a half dozen times on several different computers using both IE and Firefox.