i would go with the pentair master temp . very efficient and small dimensions make it an easy fit . it is fan assisted so you will hear a fan when its running but its not that loud . seen to many rp2100 s that either start leaking out the limit switches , pressure switch, or winterizing plug . i admit i have had to change a few thermistor on mastertemps . ive had quite a few customers that have expressed how glad they are that they have the mastertemp now