All good stuff and to summarise (as I see it)
Wind protection is essential, muffs and screen are ideal and legshields are well worth fitting too.
Buy clothing that is loose-fitting (but not too baggy).
Heated grips are
de rigeurThe one thing you shouldn't skimp on is good boots. I also use Daytona boots (roadstars) and they are the best value for money I've ever spent in biking (although they are £240+ to start with). I made the mistake of buying a pair that fitted snugly, but my second pair are a size up and they are perfect with a couple of pairs of good (thin) socks.
Eat well for energy to aid body warmth.
My personal choice for riding kit in very cold and/or wet weather is thin layers of warm clothing under a goretex layer. If it's wet I put on a one-piece nylon rainsuit. All my fancy Dainese Goretex gear works really well, but after a couple of hours of the outer being wet it starts to wick up the cuffs and ankles. It's better to delay this by wearing a thin waterproof outer layer... although it makes pee stops a trial

For my last two winter rallies I have worn a body warmer over my goretex jacket It stops the wind getting to your jacket zip and gives a little more warmth to your torso:

I use this as a sort of sacrificial layer, it catches all the crud and light rain (and still fits under the rainsuit if the rain gets heavy enough for me to put it on).
To be honest the only reason I wear my biking goretex trousers and jacket is because of the crash protection that's built in. The collar on the jacket doesn't actually do up very well, which it seems to have in common with most other modern winter motorcycle jackets.
Did anyone mention a balaclava? I use a very good one made by Dainese, it's thin enough to be comfortable under a lid, but still warm. It's also long enough to tuck into your collar to stop the worst of all draughts, that nasty cold one that gets down the back of your neck. I also have a Frank Thomas (spit!) one that is nowhere near as good so I'd say make sure you get a nice one and spend a bit more to get it if necessary.
Thin silk undergloves are great at keeping your hands warm.
From my experience I'd say that if you stop the windblast (screen, muffs, legshields, etc.) then you are more than halfway to being comfortable on the bike. Address these first then find clothing to suit.
GC