I have two of the DCP 8000's (two versions newer than the DCT's) and I have been extremely happy with them. They have been running for about three months now. They are completely quiet and the adjustability is fantastic. You can set it from 30-100% by single percent increments, which makes tuning in a herbie style overflow a breeze. I run mine somewhere between 55-60%, depending on how much evaporation I have in between water changes. If I start to hear the overflows sucking little bits of air, I just turn one or both up a percentage point and then all is well.