Help me choose a tank

[salty_firball]

Yep thats right, I need help choosing a tank. I am researching all the in's and out;s of starting a saltwater tank, im researching lights, skimmers, ro/di units etc etc but my main concern right now is the placement and the tank. I really only have one place I can put it (or want to put it) but the problem is there is an AC return on the wall. If I go with a tank with Sump I have problems of blocking the vent. Hopefully you guys can give me your input.

For reference this is my 29g on a 43" stand I built.
http://jnmstudios.com/aquarium/29g tank and stand.jpg