6080 and 6060 cannot be adjusted- they are synchronous which means they spin in sync to line frequency- 60Hz or 60 turns per second. 6100 and 6000 are controllable between 30% and 100% of output. I think you are confusing watts and volts. Tunze pumps are the lowest wattage for the flow- wattage is the big issue that is what generates heat. The 6000 is 12V, the 6100 is 19V for the US, for european customers 6100 is 20V. You should be able to find page after page on Streams if you run a search on RC. The Tunze website is being updated and so it may be down intermittently.