Rebelmarine -- I've been in your exact situation [more or less] and here's my thinking on the subject....
A semi-dry suit is good for occasional colder diving, but isn't the best answer if you're doing it regularly. Semis are flexible...you can use them with hooded vest on top or underneath, or just a hood [or no hood] if the water is warmer. I have a 5-mil Seasoft semi-dry that I pair with a pullover hooded vest, and it's pretty good for all but the coldest [sub 40 degree] for at least a couple of shorter dives. A lot will depend on your tolerance of diving in the cold. Semi-dry suits shouldn't require different weighting than a regular wetsuit of similar thickness.
Brands: Bare is a decent brand, so is Henderson. I won't say you always get what you pay for, but a cheap wetsuit is very unlikely to perform as well or last as long as a quality suit. Fit is of paramount importance, esp. with semi-dry suits, as a good close fit keeps cold water out and minimizes trapped air inside. A new wetsuit should give you a pretty full range of movement but still feel slightly too snug on dry land. They generally feel a lot better once they're in the water. They should _never_ feel too tight on the neck or chest as this will make breathing more of an effort. I would never buy a wetsuit without trying it on and getting experienced advice on how it fits.
Drysuits: I hear ya about the cost of drysuits, however if your body proportions are fairly standard, you may very well be able to find a used one, or even a loaner, at an affordable price. Sales of new but older model drysuits can also save you a lot of money, so keep an open mind on the subject. In my case, I'd have to go for a custom fit and since I'll be very unlikely to do more than a dozen cold dives [probably fewer], it just doesn't make sense for me to even try. I have to fly anywhere to do ocean diving, and I'll always choose somewhere warm or tropical for that. If I lived on or near an ocean and planned to dive there regularly, my thinking would change for sure.
