I have a Sonnet Presto and drivers in my LC. You only need the Presto extension. The other 2 System Enablers (Virtual Enabler and System 8 Enabler) are only if you want to run OS 8, and if they're installed on anything except OS 8 your Mac won't boot. So you should boot with extensions off and remove those enablers. It'll probably work after that.

Also, it doesn't work on a Color Classic with a VRAM upgrade.