Can the hulls also use the carbon fiber tow? I don't know much about the KSS method, so I'm not sure how it all works out. Perhaps use the tow first and reinforce with biaxial where required?
The cheapest NidaCore I found is from Noah Marine. (19.88 sq meter) But, nida isn't as strong as polycore.
The best epoxy price is from Aero marine. (about 40US a gallon) There is a link to Aero Marine in the boat design forum directory
The carbon tow from texas is the best for that stuff.
The biax you have better prices on too.