masocr79: Yeah I'd love such a comparison, preferably a real test /w all the right equipment so you could measue the heat dump and such. But a simple test where you use the same rig and just swap the tops to see if there's any difference would also be nice!
I'd also like to include this dual DDC top I found at watercool.de in the test.

And the dual top their developing over at forumdeluxx.de. I don't understand much but I think it's the same idéa only a high performance version.
Here's the thread, and
here's one that's probably related.