You should consult your speaker's manual or the speaker manufacturer directly. It looks to me that the 801s are designed for passive bi-amping and instructions for how to do that should be in the speaker's owner's manual. They are not designed for active bi-amping so the MEN is not needed here.
Not sure what amp you have, but you need an upper-range amp with the same voltage gain as the MC462 in order to maintain the same relative sound level. Note, voltage gain is not the same as amplifier sensitivity. If the two amps are mismatched, you can install a
simple passive adjustable attenuator between the preamp and the amp with the higher gain to rein it back to match the other amp.
Also, you should not use a tube amp for passive bi-amping, especially for the upper-range. (If you do have a tube amp, you will need some kind of simple filter up front to keep most of the bass out of that upper range tube amp.)
If you have two SS amps with identical voltage gain, you can just hook them up per the instructions. A second MC462 would be ideal but not cheap.
But the question is why do you want to do this? Is the MC462 having some kind of problem driving these speakers to the volume you want (seems unlikely)? Is there a problem with the sound quality? You didn't say, but I guess you should understand what you want to achieve.
Since you already have an amp in house, you can just try it and see what happens - if the amp is or can be gain matched to the MC462 and if the amp is solid state.
In the olden days, we had dealers who helped us with this kind of stuff.
