Your first decision is going to be whether to get a steel or aluminum plate. If you are typically diving with 8lbs or more of lead, with your heaviest tank and thinnest wetsuit in fresh water, with a standard BC, I would consider it safe to say you'll benefit from a steel plate. If you commonly need less lead than that, I'd go with a AL plate. If you're back and forth, you will almost certainly eventually end up with one of each. For me, basically I use a steel plate when diving with an AL tank and vice versa.
One of the primary advantages of the BP/W set up is weight distribution, which plays a larger role in determining your trim than anything else like wing choice. If you have a heavy steel tank in warm water, it's possible that you might trim out a little better in a AL plate and 5-6 lbs in pockets or a belt. With the weight requirements you gave, it's kind of tough to guess, at least for me. You can always approximate the weight distribution of a steel plate by putting some weight on the cambands of an AL plate, but it's not quite as nice as using the steel plate when you need the weight on your back.
I would also suggest DSS, and I would not overlook the kydex plate. Aluminum has it's downside; it does eventually corrode and the kydex plate would probably last forever like the steel plates do. One very good thing about the DSS set up is that there's no STA. I have yet to find a STA that puts the cambands where I want them. To me the top one is always too high, because it's right up there over the top bolt hole in the plate. Plus, if you go steel you probably want to avoid a STA due to your specific weighting needs.
The hammerhead plates are an excellent deal; I bought an AL one for use with steel tanks. I'm going STA-less with it, but I'm also zip-tieing my travel wing to it and adding a strip of rubber boat decking as a sort of "soft STA" and it's pretty solid. A popular set up is the hammerhead plate/oxycheq wings, but I don't know if the slots match up for use without an STA. It's easy to find out, just call them and ask for the measurement between the slots on the plate, do the same with oxycheq, and you're set. (or out of luck!) The slots do match with my venture wing, and that's not a bad wing at all.
As a few people have said, it's tough to beat the price/quality/service equation of DSS when buying a whole rig. Even though the hammerhead is a great deal, when you add up shipping from several vendors by piecing together a set up, the price rises quickly.