I'll have to agree with Cherub with iDevAffiliate. They have a lot of Affiliate training videos which are good for Affiliate Managers in general (such as yourself) and good for people that use their program.
It's more expensive than other Wordpress Affiliate plugins but for the long run, it is good.
I do recall there being an issue with it that I did not like. It may have something to do with campaigns. I like InfusionSoft becase I can have my own affiliate link and from that link, track the stats for individual campaigns by altering the link to something like domain.com/aff=101/Test2 or aff=101/NewLeads. This helps you better understand what is actually working instead of just seeing sales and not knowing exactly where they are coming from.
Having said that, if you do sell your own products, InfusionSoft is by far the way to go. You can create amazing auto-responders, send email, create affiliate applications, and many other things.
Check it out.