I don't have a lot of experience with different sizes and brands. However, when I bought my tandem, Larry Black, the owner of Mt. Airy Bikes said ditch the stock tires and use Conti 28's. I have the Ultra 3000 wire beads which can be had for under $20 each:

http://www.nashbar.com/profile.cfm?c...eid=&pagename=

They will take 125 PSI.

edit: I see the link is for the kevlar bead...even better! Our team weight is around 360 lbs.