eCommerce vs Ubercart for a specific purpose

I've been poring over eCommerce & Ubercart documentation & forum discussion and I'm generally blinded by wealth of details. I have a couple of specific things I would like to accomplish:

1) allow a user to purchase one of 4 roles, with the ability to 'upgrade' if desired. Additionally, the upgrade to the role would ideally occur as soon as the payment is complete.

Ex: Role 1 costs $10/mo, Role 2 costs an additional $10. If a user has purchased Role 1 and they want Role 2, they only get charged an extra $10 rather than $20. I imagine there must be a way to make a lesser role a default requirement for a higher role (ie to buy Role 2, you must buy Role 1)

2) Automated recurring payments, the kind that actually debit automatically rather than invoice automatically. Paypal probably won't work for this, so maybe another payment gateway?

Any insight would be appreciated - trying to piece together the answers from others queries has been mindboggling.

thanks,

Arp