Good move. Chromis usually dont last long, and often get uronema, which is not good.Yes on the sump, plan on a refugium and skimmer. I think I've eliminated the chromis.
Wait to see if you need a refugium (aka chato scrubber). A good skimmer, preferably one with a Sicce pump would do the job. I have a 25 gallon SPS cube as well, and all i run on that is filter socks changed every other day, and an Eshopps x120 skimmer (which is the perfect size for your tank) and i needed to swich to a 4 channel dosing pump, because i need to dose nitrate and phosphate along with my 2 part to keep from having 0 nitrate and 0 phosphate.