Not knowing the speaker, I would guess the 2250 amplifier and speaker setup is running less efficient than the 85/140 biamped setup. With only one amplifier connecting both high and low drivers, the overall power consumption of the speaker to produce sound has to be greater beacause of the crossover inefficiency. Most of the amp power is wasted as heat. Even though the speaker produces so many db per watt, the actual watt that gets through is maybe 20% of the power drawn.
With the biamped setup, each amp feeds the high and low drivers separately. Since the output doesn't split in the crossover and gets converted to heat, more amp output makes it to the drivers. Also, since each amp feeds either an inductor (woofer) or a capacitor (tweeter), the overall impedance is greater at lower tweeter/higher woofer frequencies - so the (bi)amps are operating at lower current outputs which enables them to better maintain their power ratings. So at lower volume levels, more of the power is actually consumed by the drivers, especially if the gain of all three amps are the same.
The 2250 will be louder at higher volume pot settings because the extra power capability will eventually push its way through to the speaker's drivers.
With the biamped setup, each amp feeds the high and low drivers separately. Since the output doesn't split in the crossover and gets converted to heat, more amp output makes it to the drivers. Also, since each amp feeds either an inductor (woofer) or a capacitor (tweeter), the overall impedance is greater at lower tweeter/higher woofer frequencies - so the (bi)amps are operating at lower current outputs which enables them to better maintain their power ratings. So at lower volume levels, more of the power is actually consumed by the drivers, especially if the gain of all three amps are the same.
The 2250 will be louder at higher volume pot settings because the extra power capability will eventually push its way through to the speaker's drivers.