Since youre upgrading, you may want to consider a CLS for added flow.tat2d was on the money about too much flow through the sump. No sense in running more through it than the skimmer will process and if the velocity is too high youll have big time bubbles. Do a search on sumps and see what folks have done.
For the CLS you can drill the tank or do an over the back desing. I personally prefer the drilled route. Its not as bad or scary as it may seem. You can drill it yourself or some LFS's will do it for you, even a glass shop or to may do it. For the design, simple is best and the CLS is the most effective way to add flow to the tank and get the most out of it from a utility stand point. Flow can really aid in keeping the tank clean. You only need one pump, there will be no electrical current in the tank and no power heads taking up space or infringing on the view of the tank!
Robert