We have a very straightforward partner/reseller scenario wherein we'll pay a fixed percentage of transaction amount.

I'm thinking the way to go is for us to get the Incentive module, do we also need the Advanced Partner Center to track and pay partner commissions?

What we want is a solution that correctly tracks the revenue and commission liability at the time of sale, and then creates the AP balance due.  Because our commission scenario is so simple, I'm sure we could do this with a little customization and some journal entries, but I'm leaning towards the module because, 1) transaction volume will be high, and 2) I like to avoid journals when possible.