well my car had a 15 amp fuse for the 'Hu/Nav' fuse. So i guess in theory its possible as an Opus 90w is fused to 10 amp max. The wiring is rated up to 15 amp or more in the car hence my 15amp fuse. All depends on your car and if you feel conifdent that way.
I myself though have a seperate wire. If you are running a wire for amps in boot and PC is in boot its a safer bet to use that. Use the HU one for powering LCD and other stuff