Yay, the alpine amp installed, and my custom harness worked as intended.
Stopped by a local installer shop, and they had everything hooked up in about an hour.
The little alpine amp hooked to the stock speakers makes a huge difference in sound quality. More than adequate for my needs. But as mentioned in other posts, the chimes and turn signal sound are quite a bit louder. I might see if I can completely disable them. Or. I might just quit using my turn signals altogether -- like everyone else on the road.
While at the shop, another guy was adding an amp and speakers to his Segway. To be expected I guess, when you live in the land of Microsoft geeks.