Assuming your speakers have a biwiring option (i.e. two sets of binding posts on each speaker, one for "highs" and one for "lows") and that you're passively biamping (i.e using the speakers' passive crossover) try this simple process:
*remove the biwiring shorter from each speakers binding posts,
*connect the pre output to each of the amps input (amps are switched off, of course, and plugged off the mains).
*then connect the tube amp outputs to the "highs" binding post on each speaker, and the bryston's outputs to the "lows" binding post, accordingly.
*check all connections are OK.
*plug in the amps (to the mains)
Switch on the amps, and you're there! However, if the amps do not have identical or very similar electrical characteristics, the sound may not be top-notch. Good luck.