I did a powerbuy in Cincy about a year ago from FloatSwitches.net. I still haven't used mine.
Their switches are rated for about 50W, but I'm not sure if that's resistive, capacitive, or inductive load. Sub 300 gph powerhead motors are usually under 25W (MJ1200's are 20W). Then again, I haven't used any of mine yet...
For any real power (especially AC), your better off wiring them to control a relay that switches the high power.
FYI: The switches that come with the Aquatronica are the same as the "new" style sold by FloatSwitches.net. The Aquatronica uses them simply as a control switch in a low voltage DC circuit and switches the appropriate AC relay per the programming.
I just recently cemented the float switch from my Aquatronica to an old algae magnet using "Marine Goop". I don't need all those stupid mounting brackets anymore - just set the magnet at the correct level, and that's it... This weekend I'll check that it's still together, and check the data log to see if the switch is working properly. Once that's determined, I'll actually use it to control my topoff and finally get away from manual topoff.