I would defiantly recommend RO/DI over a Ca reactor, to totally different items but you will get more improvement in your tank from spending money on RO/DI than a Ca reactor IMHO
i have a RO-MAN RO/DI, good unit, very slow as I'm sure they all are within reason, i got it from wonder world in rotorua, 4 stage, $390. bargain of the year (last year).
i have the aqua medic Ca reactor, it is sitting outside my sump and i have no concern about it leaking. i have found this unit needs fine adjustments about once a week, i normally do these when i do the water change, some weeks its all good though. the reg for the Co2 was the pricey bit for me ($149 HFF), i have the tunze model, very good for super fine adjustments, i got the reactor for very cheap so i have no idea what there worth.