I'm looking for a Pay per Order Affiliate management system.

I am embarking a couple of different affiliate programs, and I need a system that allows people to:

o) Sign themselves up at my website
o) Be presented with a custom URL for their link(s) back to my site
o) Give both me and them user management tools
o) Track - or at least support tracking - of their click-through return when it leads to a purchase.

Any recommendations for something like this - or something with parts of this?

Thanks,

-t