Why is having to turn it up to 1:00 a problem?
Anyway, biamping will not change things too much but will actually lower the volume. Probably not enough to notice though. The gain of the amps would have to be the same to keep things balanced. So in that respect, the volume would stay the same. However, the input impedance of the second amp will be in parallel with the first. This will put a bigger load on the preamp and lower the volume. But probably not by much. Unless you use an active crossover that will act as a buffer and might actually increase the volume depending on the gain of the crossover.
Anyway, biamping will not change things too much but will actually lower the volume. Probably not enough to notice though. The gain of the amps would have to be the same to keep things balanced. So in that respect, the volume would stay the same. However, the input impedance of the second amp will be in parallel with the first. This will put a bigger load on the preamp and lower the volume. But probably not by much. Unless you use an active crossover that will act as a buffer and might actually increase the volume depending on the gain of the crossover.