Not too much to update today....the UPS truck just dropped off the part I ordered last week...
The SyRen 10A is something one of the other builders spoke highly of, so I took the plunge. This will be wired into the dome motor, which controls which way R2's head spins. I bought this from SuperDroid Robots (http://www.superdroidrobots.com/shop/item.asp?itemid=847&catid=5).
It's a very small little device! 2 inches across!
So, another part of the electronics puzzle is here. I'll have to work on building the circuit mounting board soon so I can start wiring things in!