I have a mag 24 for my sump return to tank and it was quiet for a while then got loader, i tried cleaning it and found that it had a couple of groves in the magnet part of the impeller, i think thats what is causing the noise. I have a new impeller on order and should be in soon.
I have had no heat issues with my mag drive 24 (2400gph) but not to say you wont? Seems to be mixed reviews on heat?
Even with my halides on my tank temp is 78.