Welcome to R2R! It is hard to give broad advice because every reefer's budget, needs, and desires is different. On the pumps, in general DC is easier to tune to your system but AC is less expensive. There are very good examples of both types. Start by figuring out what you need for flow and don't forget to account for head pressure. Turnover of between 4 and 10 times your total system volume are usually recommended for a reef tank. Some go higher than that on FOWLRs. Then look at pumps that supply between 1.5 and 3 times your needed flow as a rough-guess start. I'm sure that some local reefers will chime in and don't forget that many LFSs are pretty good at their craft.