"The best" is a very vague request. If you know more about where you're headed then you can better gauge what you need.
Generally CSS/Html formatting is best with php or asp.net back end for product database and display of that database. Your pages have to be simple, quick loading in order to handle 100s if not 1000s of products and information. Your b2b site should be more text than images.
The hardest part of completing a b2b site is coordinating all the people who have a stake in it. Trust me -- I've been there before! 🙂