I got a tetratec 300 for my discus tank about 6 months ago. I really like it, the water is staying at a constant 82. It does a nice job, but can be finicky to get back to its "blooping" after a water change. The blooping is the noise it makes as it refills the storage area and then flushes. It is a unique design that I liken to a toilet tank fill and flush. The website had some very nice info on its workings. You might want to check it out.
Also, remember that the heater is sold seperately, which does make it rather expensive. The bigger sizes have 4 filter cartridges in them, I rotate them out every other month. That way you save a little money.
Seems to work for me.
They have a virtual tour at the tetra website, just look under filters to find it.