A drysuit is the only way to really enjoy a cold water dive. You can do it in a wetsuit, but you won't be underwater for long, you won't want to go deep (suit compresses, doesn't keep you warm), and you certainly won't want to do a second dive in one day...
I know you're somewhat apprehensive about not enjoying the cold water, lower visibility, local diving that you have available to you....but let me tell you what, that type of an environment is great for diving. There's a lot of life, lots of cool things to look at (wrecks, for example)....and on top of that, it makes you a very good diver. You'll go back to the tropics and be like, "wow, that was easy!"
A drysuit is a big investment....but it is a very worthwhile one. Unfortunately, with your height, buying used may not be an option, but do keep your eye out on the classifieds forum, craiglist, ebay, etc. If you can't find anything, scope out some dive shops. Find a stock suit for a tall guy, or look into having a custom one made. It will really increase your enjoyment....unlike a wetsuit (in which, you probably won't enjoy the cold water diving).