I grew up in New England, so when it came time to buy breathable waders, I bought L.L.Bean... I figured eventually, any wader, even the best, will leak, and L.L.Bean has a lifetime warantee on everything they sell... they'll fix it or replace it.
I'm 6'0, 285lbs, and I found a pair that fit me well. Call them up and get them to send you a fishing catalog (they've got lots of different catalogs) they tell you how to take measurements and get the right fit. Make sure you go a little big on the boots, though, especially if you're going to be wearing neoprene booties over your waders... my boots are the one thing I wish I had bought a little bigger. I bought their model that has the rubber soles with the little round raised areas on them, and they work well.

-N.