Ok here's a pic of what I was running under my 55g tank, and I hope to utilize a similiar concept under my new 90g reef tank.
The sump was built out of a 20g long tank with 1/4" baffles from a design I saw on Melev's site. The refugium was originally in the middle section and the small glass baffle kept the sand out of the return pump. However, After a while I began to dislike the fluctuating levels in the fuge section, so I opted for a gravity fed seperated fuge (10-15g tote from Lowes). 25% of the water from my display tank is diverted via a ballvalve into the fuge, which gravity feeds into the return section. Also I use a HOB filter with 1-1" bulkhead, connected to 1-1/2" PVC.