Listen, HOLD IT. Check out some bad experiences of the Linksys dual wan router users first!
http://www.google.com/search?q=linksys+RT042+experience
Try to google "dual wan router review" first.
After I read Joe Mehaffy's review, I finally bought a Peplink Balance 300 a year ago. It has been working flawlessly until now! The greatest thing is that I don't even notice its existence after it was set up. The Peplink people also keep releasing firmware updates.
Don't waste your time and money on the crap.