Definitely use high quality double-butted spokes. The spokes are what make the wheel. Building a strong hoop or a strong hub is simple enough, and you can't go wrong with deep Vs and any decent hub. If you skimp on the spokes, you're pretty much asking for trouble.

Stick with stainless steel DT Swiss spokes and good brass nipples and you should be fine as long as you find a good builder.

Jim at the Hiawatha Cyclery in Minneapolis builds killer wheels for big guys somewhat regularly. There's probably a good shop closer to your area, but if you don't know who to talk to, give Jim a call or email and ask for his advice. He'll give it to you straight and I know he builds great wheels.