DSB: I did some research on DSB and found two schools of thought. The Anthony Calfo 'DSB in a bucket' used purely for nitrate reduction. He still recommends aggressive skimming and I believe other filtration - live rock, carbon, etc... My feeling is this is an option to consider once a tank is running for a while and still has high nitrates. The other school of thought is the Ron Shimek DSB which is intended as the primary filtration method. He recommends a DSB in the display tank so that it is large enough and is taken care of. There are some good examples of this type of tank but it seemed to me that a relatively small percentage of successful tanks are run this way. I think you have to stock lighter and at a slower rate.
Also here is some research that indicates deep sand beds are beneficial.
http://www.advancedaquarist.com/2005/7/aafeature
I've decided to go skimmer + shallow sand bed. Take all this with a grain of salt, this is my first tank.