Fortunately, almost all of the ca rxtors are pretty good. I guess the manufacture figure that they can't get a sucker to buy junk reactor since if you need to get one, you pretty much know what you are doing.
However, this also means that they can be a bit difficult to setup and use if you don't know what to look for. Ask around and see the feedback for ease of use. You can talk to the people in reef hardware stores (online ones such as most of RDO sponsors like PremiumAquatics, MarineDepot, etc. are better than most LFS, IMO), and they will give you some suggestion.