How about a Tunze 9002 . I have one in a 10 gallon sump on a 55 gallon tank. The tank has softies in it and only 3 small to medium fish. It has been going on 3 years now and I have never had a problem. It's rated up-to 52 gallons for a litely stocked tanked. Hope this helps and good luck on your search.
SWC120 cone, i have one for my 60 cube build. they are not over priced and get good reviews, small footprint as well. I have seen a few in 10 gal sumps, i was going to use mine in a 10 g sump but changed to a 20 high at the last min.