FYI... required reading in this one. "hashrate isn't everything":
https://litecointalk.org/index.php?topic=2310.45

I did some math and I'm getting the following WU %'s for cards 0-3: 90%, 88%, 86%, 88%. That's 640, 624, 622 & 618 WU/s. Not to shabby, but also very interesting... because my GPU 0 is outperforming my GPU 2, even though GPU 2 has 17Kh/s more than GPU 0.

Also... this http://www.overclock.net/t/1461916/tutorial-ultimate-guide-to-tweaking-amd-cgminer-3-7-2-kalroth-edition-sgminer-instructions-included-aswell-get-the-most-hash-out-of-your-gpu

Time to tweak again.