Thoughts on SS bass. Tube mid and high tube pre

The Tannoy Monitor Gold's crossover is in the midrange - 1000hz.
The tweeter and base are aligned with the crossover and physical position such that at the cross over point the tweeter and base are perfectly in sync with both phase and time - hence the name "dual concentric".  Unlike other dual concentric drivers, this phase coherency at the crossover is the key to the Tannoy sound.

If you use different amplifiers for the tweeter and base, they will have different time constants and you will destroy the phase coherence at the crossover point. You will defeat the whole purpose of the Tannoy design.

You should stick to one amp, unless you want to try the same amps top and bottom.

Personally on my 15" Monitor Golds ( Belvedere Seniors & GRF Professionals ) I prefer high power solid state to tubes as the Tannoy drivers are medium efficiency, as you increase volume they soak up more power at an increasing rate.

First Watt amps voiced with Tannoy, probably the best amp for them if you want killer SS amp.

If you are into having a really expensive, really cool looking system that soaks up money and space far out of all proportion to how good it sounds, you could scarcely dream of a better method than bi-amping. Bi-wiring is for chumps. EQ? Spare me. Bi-amping rules. 

In truth only one thing beats bi-amping. Tri-amping. Be sure to use mono-blocks. Preferably with outboard power supplies. Because as everyone knows the more boxes and wires the better it sounds.

Based on what Dover suggests, if you were to bi-amp, why not run a separate amplifier to the Heil tweeter? While that would do nothing for power demands in the bass, it would at least reduce the effect on impedance of running the supertweeter in parallel with the Tannoy. (The two speakers in parallel reduce the net impedance seen by the amp, as I am sure you know.) The resulting increase in the impedance seen by the tube amplifier can only help it to cope with power demands. (Tubes do better as regards both power output and distortion when interfaced with higher impedance speakers as compared to the net of 4 ohms you may be dealing with now.) Also, or as an alternative, add a subwoofer with its own amplification.

I would think very carefully before doing this. Your speakers are the limiting factor here. I would go with Tekton. They have more drivers. The Tekton Moab for example has 17 drivers. So you could have 17 amps. If that's not enough the Ulfberht has 21. If you were to go monoblock that would be 42 amps. The only problem I can think of, bi is 2, tri is 3, octo is 8, but I don't know the word for 21.