Ask HN: What shopping cart system do you use and why?

Hi again.

For our startup we also need a shopping cart that is:

Capable of recurring payments with Paypal and Authorize.net or the new Canadian Paypal Website Payments Pro.

Sends all the needed emails about expiring credit cards, missed payments etc, branded as our company, coming from our email addresses.

Preferably is something we host ourselves, as opposed to a hosted solution.

Can allow us to upgrade and downgrade accounts such as from Gold to Silver level, without having to cancel one account and start another.

Has a built in area for customers to update their information, branded to our site.

Is relatively easy to use and flexible.

Any suggestions? I'm having a hard time finding anything.

Thank you!