From what I've read in aquarium forums, these pumps run as hot as they come. I've seen a lot of complaints about the large amount of heat dumped into the water. Quiet tho, apparently.
In contrast, a pump like the Hydrothruster (disc?) with an isolated impeller assembly adds no motor heat into the water.
The pump I just got is the
Custom Sealife Velocity T3, very high head capacity. Noise less than 30dBA. I got it in barely-used condition for $120. I am going to start testing it as soon as I get my current WC system disassembled. I'll post some results here (subjective).