I would interpret the question as referring to continuing to use the two amps in a vertical biamp configuration, but using EL34's in the channel of each amp which drives the mids/highs, and KT88's in the channel of each amp which drives the lows.
If so, a concern I would have is that the gains of the two channels would differ to a significant degree, resulting in a tonal imbalance. Unless, that is, the crossover network can somehow be adjusted to compensate. Or if you're lucky enough that using the 4 ohm tap on one channel and the 8 ohm tap on the other channel would happen to compensate sufficiently closely.
Regards,
-- Al
If so, a concern I would have is that the gains of the two channels would differ to a significant degree, resulting in a tonal imbalance. Unless, that is, the crossover network can somehow be adjusted to compensate. Or if you're lucky enough that using the 4 ohm tap on one channel and the 8 ohm tap on the other channel would happen to compensate sufficiently closely.
Regards,
-- Al