Hi CF,
here is a link to my DIY skimmer. It's big, it's ugly and it works (Three check marks in the plus column).
http://www.canreef.com/vbulletin/showthread.php?t=28197
If you buy a cannister I might recommend not going for the FX-5. As suggested, the key in SW is to clean your filters regularly to export the detritus. The FX-5 is a great filter but it is also heavy and can be awkward to clean if you have a small sink. Look at a Fluval 405 perhaps. Still a good choice and much easier to work with.