Sedond is right about the active cross-over. Only use this if the internal cross-over has been disabled (bipassed). I'm using an active cross-over, but my speakers were designed to use an active cross-over--in fact, if bi-amped they must use an active cross-over.
Using one stereo amp for left and right is not a bad idea at all. There is less cross talk in this set-up because one amp is seeing the left channel--rather than two different channels. There will be differences due to the high pass vs low pass, but they will be harmonious and I would not see cross talk as being much of an issue--if any. I presume you are doing this to get each amp very close to the speaker and run as short a speaker cable as possible--if that's the case--good choice.
Lastly, ohm rating. I'm going to go out on a limb here and guess you have a nominal impedance speaker (4 ohms), but I'm guessing you are asking this question because it has a tendancy to go very low in impedance, and you think bi-amping will help this problem. As previously posted, only the manufacturer of the speaker can give you this information. It will be different for the high end and low end. I have a pair of Martin Logan Monolith IIs. They have very low impedance from the panel. The bass has a reasonable impedance--4 ohms and probably doesn't dip much below that, but the problem with single amps on this speaker is the impedance drops from the panel, then a bass drum kicks in and there's no umpf left in the amp (umpf is a technical term). By bi-amping you isolate the demands of the woofer vs the low imedance from the panel. I don't know if you own MLs or other speakers with similar characteristics--but I said I was going on on a limb here. If this is the issue you are trying to address--it should work very well--it did for me.
Using one stereo amp for left and right is not a bad idea at all. There is less cross talk in this set-up because one amp is seeing the left channel--rather than two different channels. There will be differences due to the high pass vs low pass, but they will be harmonious and I would not see cross talk as being much of an issue--if any. I presume you are doing this to get each amp very close to the speaker and run as short a speaker cable as possible--if that's the case--good choice.
Lastly, ohm rating. I'm going to go out on a limb here and guess you have a nominal impedance speaker (4 ohms), but I'm guessing you are asking this question because it has a tendancy to go very low in impedance, and you think bi-amping will help this problem. As previously posted, only the manufacturer of the speaker can give you this information. It will be different for the high end and low end. I have a pair of Martin Logan Monolith IIs. They have very low impedance from the panel. The bass has a reasonable impedance--4 ohms and probably doesn't dip much below that, but the problem with single amps on this speaker is the impedance drops from the panel, then a bass drum kicks in and there's no umpf left in the amp (umpf is a technical term). By bi-amping you isolate the demands of the woofer vs the low imedance from the panel. I don't know if you own MLs or other speakers with similar characteristics--but I said I was going on on a limb here. If this is the issue you are trying to address--it should work very well--it did for me.