I've had a Gerbings jacket liner for a few years now - fantastic bit of kit. You need the controller though, otherwise its just too hot. I went for the Gerbings cos it has sleeves and a collar that are also heated.
I tend to have it set so that I don't feel any cold coming through, but don't feel any extra heat from the jacket either - typically this means no more than about half-way on the adjuster which I keep in a pocket so not too easy to adjust once underway although you can get a bike mounted one.
The Strom is well up to the extra drain - I have a k7x so with no ABS and 400W to play with there's loads to spare.
Only thing you need to do is keep remindng yerself its icy out there as all that warmth can lull you a bit.....

)
Iggy