All clones are essentially certain Mac models in different cases. There were never any PowerBook clones, but a couple of firms in the early 90s reboxed compact Macs in portable cases (Colby, Dynamac, and Outbound machines), which are all hard to find nowadays.

Anyway, the PowerComputing boxes were typically the higher end of the clone hierarchy, so you're pretty safe getting any of them. Check everymac.com's PowerComputing page for specific info.

I'd definitely pick up some of the PowerTower Pros; I only have one of them.