I am testing my units tonight, received 4 units of the 6450. The 6610 is a lot louder, but the 6450 makes a vibrating sound. I think I need to replace the fan, then it should be super quiet.I have the 6450-24p and for me, the switch is very quiet; and uses about 30-35watts. A friend was asking about the 6610-48p. Hard question to answer, but "now many times louder is the 6610-48p vs the 6450 "?