Correct, that would be bi-"amping", not bi-wiring. You would still need some way to control the outboard amp. Either level controls on the amp itself or an outboard crossover. Since the power ratings are so different, you'll need to balance them out.
Usually, biamping involves the same amps or running them through a crossover.
Usually, biamping involves the same amps or running them through a crossover.