Affiliate management software for SaaS

Any one have any recommendations for an off the shelf affiliate management software for a Basecamp-like application?

It needs to support

1. multiple tiers of affiliates

2. ability to change payouts when users change to a new plan

3. provide automatic affiliate sign up

4. integration with credit card providers

5. provide payout reports so that we could write out cheques

I had a look at Post Affiliate Pro, and it does everything except #2.

Thanks