Tank Size/Shape Opinion needed

[ScubaSteve]

So it looks like I'm moving to a new place in a month and this has me thinking I might create a new tank rather than sticking with the ol' 20G. Now, the amount for room I actually have to work with still needs to be worked out but I want to get everyone's opinion on some tank sizes and shapes that can work with equipment I have.

I because I am a poor grad student I have to rent apartments and so I'm usually limited to a maximum size of about 30 gallons; the tank I am looking to change is 20G and it's just... too small.

I have always been a fan of the shallow square tanks (not a cube). I think they're cool because you have some depth (width-wise) to work with and do some nice 'scaping and you can look down into them from above. I am curious though if my light will work with this shape of a tank. Right now I have a 24" aqualight pro 150W with 2-65W actinics. Do you think the light will be alright over a square shape or is the light distribution going to suck?

Also, is there anyone out there using shallow square tanks as a DT? How do you feel about them?