Hi there. For some really good info on sumps, check out
http://www.melevsreef.com/. He has a lists of all the sumps he has built and has a brief description of each. Just take a gander there and see what fits in the space you have.
BioBalls are an "old school" method of biological filtration. I have never used this method, so I can't really comment first hand as to it effectiveness, but currently the trend is live rock and sand as your major source of filtration. Protien skimmers can be run inline with sumps and many people do it.
Reefs are trickier than fish only tanks as corals and such are must less tolerant to poor water conditions. Therefore a lot of reefers spend a lot of time tweaking their water and making sure the conditions are up to snuff. Of course, with reefs, there is added cost in lighting and pumps, ect.
Though I've never shopped at Salt Water Fantasies, I've heard very mixed things about them. Ususally he has very cheap prices and sometimes hard to find fish, but usually there are not the best of specimines (or so I've heard). If you have any more questions, just ask.
Cheers.