I don't believe the amp does supply power to the active spoiler. Apart from that being a very strange way for Toyota to wire things up, if you look at the diagrams linked to here:
http://www.mkivsupraownersclub.com/f...ghlight=active there is no connection between the two.
I think what you're doing by eliminating the amp and excess wiring is probably a good way to go, just make sure nobody has used any of those PITA Scotch-Lok connectors, as they are usually responsible for intermittant connections if they have been used.