Nanacast. Bar none.

But not if pricing is the issue... I think they're more or less on par with 1SC for pricing. But they deliver a bigger punch.

Alternatively, look into RAP which is a one time fee (fairly low cost). Those are the 2 solutions I use.

On my site, I posted various resources etc I use. There'se a walk through vid with about 10 minute talk of shopping cart / aff management platforms. Might be of use: http://www.robtoth.com/genieadvantage.htm