<font color='#000080'>Hi
I have a Helios 9 with 10Watt Proteus HID head.
They work very well and I have loads of burn time available. The canister is slim and has never leaked. The switch is robust and easy to find underwater (I tend to switch the light off on ascent and on when about to descend).
I would recommend the 18W head though as the Proteus has a tendency to break the testube bit of the bulb (still works without the test tube bit though) and the twist focus thing sometimes turns my light off so I tend to leave it at the smallest beam. It is more compact though and I find that to be an advantage when clipping off on the ascent, it doesn't dangle so much.
I am upgrading shortly to a 13.5 and 18 watt head though because the 18w is a better lighthead. If you use the E/O leads you can replace the bulb underwater for example and the beam is much brighter and thicker. I'll have the 9 as a spare
They are great torches though and I would never dive without one now. Once you get used to light signals you can never go back.
Hope that helps
Andy