A sump is not a wet/dry filter. That's something used primarily for fish only tanks, due to the filter not converting nitrate to nitrogen gas. For a reef tank you would want to have very low to no nitrate.
A sump is basically just another container of water. What you put in it varies, per hobbyist.
When we are talking powerheads, do you mean a pump that returns water to the sump, or pumps that sit in the display and are used to increase flow?
If it's return pumps, Danner mag drives, Quiet One's, and Eheims seem to be the most commonly used. Don't skimp on one of these, since your tank depends on it.
As for the gph
of the pump, that would depend on what you are feeding in your sump.
In other words, if your sump has a protein skimmer in it that has a 500gph pump on it, you want to send it at least 500 gph
(after head loss) for maximum efficiency.
If we are talking power heads inside the tank for flow, Many people like Hydor Koralias, Aqueon power heads, and the uber expensive "Ecotech Vortech".
The protein skimmers I like that aren't ridiculously overpriced are Reef Octopus, Bubble Magus, ASM (the new cones, not the old models), Sea Side Aquatics, Vertex, and lastly, JNS.