i dont have a 1048 but i have heard that they are pretty silent and put off very little heat. mario reviewed it on wc101.com but that part of the site seems to be down due to server problems wc101 is having. i have the 1250, the 1048's bigger brother and its pretty quiet and doesnt put out much heat.
Yo. I've got the 1046 and 1250. I ran the 1250 in a sink full of water and could only hear the water swelling where it was pumping so fast. Definitely a good pump. My freind who's into marine tropical aquarium's ran one for a year, 24/7 and thought he'd better turn it off and clean it. Took it apart, and all the bits were fine. Put it back together, and it's still going strong a year later.