Gerbing is probably some of the best out there, and has good customer support as well...if I were purchasing, I would go with them, unless they offered me a good deal on the HD stuff, which may be made by Gerbing anyhow.
Like Candy mentioned, there are a lot of good clothing items out on the market to keep one warm. I can ride down to temps in the upper 20's to mid 30's without heated gear, and be comfortable on my SEUC, but do have heated seat and grips. Cotton is useless as an effective insulator for your body, and will cause serious problems if it gets the least bit damp in cold weather. Look for long underwear, underwear, and base layers made of Capilene (Patagonia), or polypropolene like UnderArmour and similar products. You'd be amazed the difference this kind of product will make. Also look for fleece midweight jackets/tops with Gore Windstopper in them...a midweight fleece jacket is not bulky under your leathers, and the Windstopper fleece adds another dimension to the layer, and is nice to wear after riding and just hanging out.
With all the newer materials out there now, there is no need to be "bound up" in layer upon layer of clothing, as the newer tech stuff is MUCH more efficient in insulating your body. Go to a good store devoted to backpacking/mountaineering and take a look around...even if you don't buy, you'll get some good ideas. I've got stuff like this from 20 years ago, and it still functions like new...it costs more, but it lasts forever.