OK, you're using the U360 onboard encoders.
U-Trak trackball has a USB encoder you can order with it.
Info here.

If you're getting the SpinTrak, it also has an encoder you can order with it.
Info here.
ORIf you're getting the TurboTwist 2 from GGG, it also has an encoder you can order with it.
Info here.

My current setup uses a U-Trak and a TT2. They work great together.
The main thing to remember is that you want separate encoders for your trackball and spinner for 2 reasons:
1. There is a problem with the way that
Windows handles the Z-axis. One optical transition gives 4 steps.
2. If you accidently bump the other control, the encoder will assume that is the one you want to use and lock out the other for several seconds. Separate encoders means no lockout.
You may not need/want the Opti-Pac, depending on how you configure your software.
The two questions that I have are:
-- What frontend (MALA, Hyperspin, etc.) are you planning on using?
-- What if any admin buttons (P1 Coin, P1 Start, P2 Coin, P2 Start, Escape, Pause, Enter, Tab/Menu, etc.) do you want?
Scott