Ideally all RAM would be of the same make and speed. The further you get from the ideal the more likely problems become. I say "more likely", but in real life, you could have every stick from a different maker and still have no problems (I see computers coming in for repair like that--they're being repaired for viruses or dog fur, not RAM issues).

But me, I like all my RAM to match.

Thank you, Chris! I really appreciate your expert opinion!

I would be nervous about it trying to OC the lower level RAM, but it theoretically shouldn't.

The BIOS should report the auto detected speed, if it configures the speed to high, it can be overridden manually too. That memtest86 I linked to before, should be run regardless.

Thanks guys-
I lost internet for awhile this afternoon, and didn't get a chance to post that I decided to just order two sets and install 6 matched sticks, giving me 24GB. I also ordered a USB 3.0 card as they weren't available from Dell at the time of ordering.

And I also didn't get a chance to post that, though Dell still has the status of the computer as being built, it arrived this afternoon!

Look closely, maybe it's still being assembled my nano-machines.

That's the way I would have gone with the RAM too. Just put the rest on eBay, and someone looking to upgrade their Dell will pick it up.

Chris, I installed the 24GB of RAM and, as per your suggestion ran memtest86 which showed everything to be "good to go".

Now I have to put in a USB 3.0 card I bought and an extra 2TB HD I've had sitting on a shelf....

Just wanted to say thanks again!

Does memtest86 work on AMD machines?