depending on what kinds or corals you want to keep it can vary. If you just want softies leathers and such, 3wts a gallon of PC can be enough, but if you want hard corals like LPS SPS you need MHs. Ive never dealt with LPS and SPS corals much but you need 6-7wts minium for those, Im not 100% sure on that.
As for a sump, what are you wanting to do with one? Just for more water volume and a place to put your heaters and other equipment. Or do you want an insump skimmer and a refugium. Ive build lots of sumps for myself and friends so get back with what you want to do.