So the only thing providing boundaries for the size of you new tank is what your existing equipment can handle. So your lights, 6 t-5's can do the job but only if you have great reflectors for each bulb and are able to replace them often, otherwise a metal halide or two in addition would make it much easier for you to maintain sps. The next thing to consider which might even be more important than light is your filtration ability. What kind of skimmer do you have, and do you have any others type of filtration methods like carbon, canister, or refugium? The final thing is water flow. I'm sure you will need to increase the number of pumps/powerheads you have for a new tank. Also I'd advise against getting a bow front tank, I used to have a 90 gallon bow and the shape I thought to be a big pain when it comes to aquascaping. I think breeder style tanks are much better for ease and asethetics. So lower height and deeper width.