paid event registration

I'd like to start a discussion here regarding some functionality that I am looking for in a Drupal/Ubercart Registration system. The Ubercart registration is not absolutely required, but may allow for easier management of the backend.

I'd like to be able to create events that people can register for, but before the registration is finalized the event must reach a certain threshold of registrants. With that I'd like for the credit cards to be held and batch processed once the threshold is met, and any registrations from then on are run immediately upon checkout.

Hello all-

Anyone have experience with the Signup Integration module and Ubercart in Drupal 6? I can't seem to get it to work. I would love to have someone take a peek or point me in the direction of additional training/resources.

Overall, I am interested in a paid event registration solution so if someone else has a better idea, I am interested.

Thanks!
Tara