I agree that Hagen makes good products. I have 2 heaters by Hagen and a filter by Hagen (yet another filter by Hagen will be delivered to me on Monday as well). I've been using all of these Hagen products for 2.5 - 3 years now, and not a problem so far. The heaters distribute the heat extremely well and evenly, and they keep the temperature very stable. The only downside is that they're glass heaters so if you're not careful you can break them easily. For this reason, I ordered Visi-Therm Stelaths for my next tank (they're not glass). I hope they'll be as good as Hagen filters are, in terms of temperature distribution and its stability. As for the filters (I've Aqua Clear) ... they're PERFECT. No bypass of water, large, sturdy, and durable filter media, and great water flow.
Yes I love hagen products too, all their air equipment and filter I'v used only A+ about them . their biggest model is only 137gph so I was wondering a little. I have no doubt it will be good, i'm more worried about the water flow because I don't want a strong current in my 5.5 gallon for spikey and for the plants. I'm debating between this and the red sea nano filter, I might go with the red sea nano as it has adjustable flow and I have a light fish load the underfiltering won't be a problem.