Soundhound, thanks for the reply.
Here are some informations from a review.

Each speaker has two 9" woofers (actual measurement), four 3" x 6" foil planar drivers and two 1" spiral ribbon tweeters. Impedance is a "steady" 4 Ohms (3.6 minimum), and due to the ribbons, primarily resistive above the 166 Hz crossover point. Crossover slopes are 6 dB/octave, and efficiency is 90 dB.

For biamping VMPS suggests the following.

By switching the toggle to the UP position it is possible to biwire or biamp the system with no additional outboard crossover. The woofer is placed on one circuit accessible through the UPPER input terminals only. The ribbon mids and tweeters are accessible through the LOWER set of input terminals,
Biamping with non-identical amps, particularly solid state bass amps plus low-power mid/treble tube amplification, requires level matching by the mid/treble amp. Most tube amps have higher input sensitivity than solid state amps. It is advisable to use a mid/treble tube amp with input level controls. If your amp lacks such controls a passive input level control (also called a passive preamp) can be used in front of the amp inputs to match levels by turning down the mid/treble amp relative to the bass.

I am planning on using 2 channels from 770 for the woofers and ARC VT100 for the mids and tweeter. The specs on VT100 is as follows:

POWER OUTPUT: 100 watts per channel continuous from 20Hz to 20kHz. 1kHz total harmonic distortion typically 1% at 100 watts, below .05% at 1 watt. Approximate actual power available at "clipping" 110 watts (1kHz).

POWER BANDWIDTH: (-3dB points) 15Hz to 80kHz.

FREQUENCY RESPONSE: (-3dB points at 1 watt) 1Hz to 100 kHz.

INPUT SENSITIVITY: 1.9V RMS (Bal or SE) for rated output. (23.5 dB gain into 8 ohms.)
What is the input sensitivity for 770?

INPUT IMPEDANCE: 200K ohms Balanced, 100K ohms Single-ended.
OUTPUT TAPS: 8 ohms, 4 ohms.

OUTPUT REGULATION: Approximately 0.8dB 8 ohm load to open circuit (Damping factor approximately 11).

OVERALL NEGATIVE FEEDBACK: 10dB.

SLEW RATE: 15 volts/microsecond.

RISE TIME: 3 microseconds.

It looks like I need a passive preamp for the tube amp. What would you suggest? Since 770 is not balanced, I would use the single ended outputs on the ARC amp, right?
I don't recall 770 having output taps for 4 or 8 ohms but it shoudn't have any trouble driving 4 ohms load, right?

I don't want to blow any drivers. So, any advice you can think of would be very much appreciated. It may be that the whole thing would sound terrible and all the components are mismatched. The "audiophiles" don't use 770 in reviwing these speakers and probably poo poo on my trying, but I am banking on it being good enough to drive the woofers. Out of my ignorance, I am willing to give it a try. Afterall, isn't there some Sissypussian (sp?) joy in endless tweaking.