I've had the Koralia 4s, Tunze 6045s, Tunze 6055s, homemade MaxiJet Mods, Vortechs and SureFlow mod.
The SureFlow (and homemade) puts out more water than any of the above with the exception of the Vortech. I think it looks rather sleek personally and doesn't look crappy at all. Mine ran silent for a week, but later developed a very noticable hum in the tank, but no more so that the Vortech or 6055s. Once you add on a magnet, the cost goes up and makes them value wise really behind the Koralias.
In the end, the Koralias are hard to beat. The Tunzes put out a weak flow (well the 6055 can throw around water) by comparison but they are smaller and are more versatile when it comes to placement. Vortechs are top of the line, but at full speed a bit noisey for my tastes however the noise doesn't bother most people.
I have been really impressed with the 6055s but that is a different league as well.