I use an AquaC Ev http://www.proteinskimmer.com/ and I love it. It's powerful, quiet, and easy to clean. I've used it in the sump and outside of the sump.
I second the vote for Aqua-C I have had the EV-90 and the EV-120 and both have been great although the EV-120 is much better due to teh improvements they made in the design.
