What you intended to do is passive horizontal bi-amping, if using two different stereo tube amp, you need a volume control for gain matching if both amp has different gain.
If both stereo tube amp are identical, vertical bi-amping is better, you can use one amp to drive Right speaker tweeter and woofer, use the other amp to drive Left speaker.
A 'Y' interconnect cable should work in most case.
If both stereo tube amp are identical, vertical bi-amping is better, you can use one amp to drive Right speaker tweeter and woofer, use the other amp to drive Left speaker.
A 'Y' interconnect cable should work in most case.