I bought the 600 thermo model and did every modification suggested by the Pimp my Filter guy.
-replaced the 1/2" intake pipe within the prefilter chamber with larger diameter 3/4" pipe and drilled larger and more holes. In addition, replaced finer foam with the coarser blue foam.
- I moved the orange medium foam from the top to the bottom chamber( first chamber after pre filter) and topped that with finer filter media, last one being 100 micron. So now flow goes through course, medium, and the fine before hitting bio media.
-in the middle trays I replaced the sponges and plastic bio material with Hydroton clay media. And in the top tray another layer of mechanical. A layer of carbon pad or poly filter is an option here too.
- finally I drilled larger holes in the spray bar.
Some caveats. So far it's working great but its only been seven weeks. I'm sure I increased the flow substantially but I did not measure it; I do plan on doing that. Also, some have questioned whether Hydroton is an efficient bio media, but I've had success with it and it's dirt cheap and widely available. I can tell you that it cycled my new Amazonia Light/ power sand 50 gallon tank in 2.5 weeks with the help of some seeded Hydroton from another tank. I am monitoring Nitrates closely. So far readings are staying steady at 25-30.
Regarding the heater, it works well and holds a steady temperature. I think the mods may have made the filter a little noisier; their is a humm.
Did I make it better with my mods? I'm not sure yet, I don't have enough experience with different cannisters to say, it's the first one I've owned. I've been a reef/ sump guy for the past couple decades and used a sump on my first planted tank. All in all, I'm happy with it so far.