On thing to think about is how you will access the tank.
On my 180, it has a custom canopy that the original owner built. While beautiful, to access the tank, I have to open the front doors. If I have to access the back corners of the tank, I either have to stick my head in with the lights, or remove the canopy completely (hard to do the way the power cords for the lights were designed).
I have a 80 with a stock canopy that opens up like a piano lid. Great access; but, I have to make sure that the whole thing doesn't slam down and break the lights.
You'll have to think about what style works best for you.
Best of luck,
Roy