Before I upgraded my amps to ones that had built-in crossovers, I tried this myself. Essentially what you're doing is trying to use the empeg's EQ as a crossover.

This didn't work well when I tried it, and I recommend against it.

If your amplifier has an adjustable crossover, I suggest you use it instead. If it doesn't have a crossover, I suggest you use something like these inexpensive inline crossovers instead.