A few Q's for the more Knowledgable.

[whatcaneyedo]

Head loss calculator http://reefcentral.com/index.php/head-loss-calculator
Melev's Reef - Sumps http://www.melevsreef.com/links.html

"As you suggest a sump for such a small tank I'm throw." What?

A four bulb T5 would work well or I'd go with a 150W MH. Even a single 250W for a shallow nano-tank would be overkill.

Eheim pumps are an excellent small pump.

A two drain overflow is typically called a Herbie Overflow and will fit a 20gal tank much easier than a bean-animal which are pretty elaborate and require three holes.