Bert:
We have tried the gravel vac on the magnum 350 and the HOT Magnum and do not like it. With a floss sleave on the micro cartridge, the micro certridge clogged in about 3 minutes. The filter is not easly cleaned and can't be cleaned back to original condition. They are also expesive the best price I have found is apx. $9.00 each. We use ours only for a mech. filter with the charcoal and a floss sleve.
Since we have 2 Emperor 400's (bio-wheel) we haven't tried the bio-wheel accessory.
I have never used a python.
I use a Vortex XL diatom filter to clean the gravel with a siphon on the intake. Also use a recirculation valve. Not only does it stay clog free it outputs incredably clear water back to the tank. I then allow it to run for a couple hours to scrub the water. When finished just shake it, remove the jar, and pour the crud down the toilet. Rinse off the filter element and your good to go. By the way a diatom XL cost less than a Magnum 350 see (petsmart.com)
Vortex also mfg. a diatomous earth / charcoal mix for their filters. I havent tried it yet so I dont know how well it performs.