Yeah people at xtremesystems are always saying 'Nah go with the 50z, not the 650, it's quieter and puts less heat into the water', buuuut yeah, the few people who I know own the MCP650, say they can't even hear the dang thing and now you say the same, because what are the chances of you hearing that thing over a few fans? Some people are just anal...all I know is it'll sure be a helluva lot quieter than my tornado, and as far as heat into the water goes, I doubts it's even 0.5C,