Crossover cap value?

Basically - I want to copy what Magnepan did with their XO-1 electronic crossover box. This simply sends the full spectrum audio signal to the bass amp ( which is low pass filtered post amp ) and allows you to roll off the bass ( high pass)ahead of the input of the amps driving the mid/tweeter panels in a T-3A or T-4. Have set these up for a few folks over the years and would like to accomplish the same effect with my system. My scheme is as follows:
Paradym Studio 20-S2 are described as having a 3rd. order electro-acoustic crossover at 1.5kHz. These speakers have a dual binding post set up for bi-amping or bi-wiring. I would like to run my Hafler DH-120 into the bass speaker ( no problem low pass filtered by the existing passive crossover) and my Hafler SE-120 into the tweeter. What I'd like to do is roll the bass out of the input of the SE-120 tweeter amp (high pass filter). SE-120 's input impedance is 22kOhm.
Q-1: I'm wondering if I want to get close to 1.5kHz for a selected bass roll off/ high pass or should I go down a octave or two? Since a single cap gives me a 6db/octave filter( not exactly a infinite slope) - should I calculate the bass roll off/high pass for 1.5 kHz, 750 or 275 ?
Q-2: What is the formula to determine the cap value for various frequencies into a 22kOhm input impedance.
My goal in all this is to unload the tweeter amp from having to deal with the current hungry demands of deep bass - hopefully gaining a little more clarity at higher volume levels from what are admitidly small ( but sweet sounding) amps. And still use both sections of the excellent passive crossovers built into the Studio 20.
Or does this come under the catagory of "has inhaled too much solder flux" ?