i also have a danner mag 5, i got it from work, nice and cheap (of the five finger kind)
and i have a aqua clear cap 1800.
i got these two pumps to see which was better. in reading the specs, the danner puts out 45 watts of heat, the 1800 puts out 29 watts.
danner 5 puts 500 gph and the 1800 628 both at 0 head.
danner 250 at 5 feet and 1800 315.
so unless the 1800 is unberably loud, ill have to go with it.
BTW just waiting on a block to set up my water cooling rig