Yup, I've got the "6-1" one running on my 120g. I'm happy with it...it's really as easy as everyone says, and does an excellent job.
It's hard to tell the difference between the Euro-reef and the Southbay (at least for me it is). The Southbays use the same pump, same impeller, and same overall design. I think the materials they use in the Southbay are comparable to the Euro-reefs (though my Southbay came with some cool smoke acrylic for the neck of the skimmer to impede algae growth).
I'd definitely recommend them...I actually went to buy a Euro-reef, but they were out of stock at the time (actually, everyone seemed to be out of stock at the time) and Jeff's suggested the Southbay.
Hope this helps, and good luck.
Thomas