[Pescador]

Hi
I think 2x4's should be fine, on mine I used a metal stand but I added extra studs in the wall where the tank will go and put the plywood over the stand and the top of the wall in the opening so the tank could sit flush with the front of the wall.

You can make the middle legs of the stand removable with "L" brackets
so you can remove the sump if you have to.

Your still on the low end of amount of lighting so I don't think you'll have to worry about putting softies under too much light. Depends on the depth of your tank though. Assuming it's 21"-24" deep.

If your building the wall from scratch it's great to be able to plan power outlets, blocking for mounting equipment, even running water and R/O lines. If you haven't already think about using cement board or bath board instead of drywall.