I suspect that wouldn't work out well. The impedance of the speaker is spec'd as 8 ohms nominal, 4 ohms minimum. I would suspect that the impedance is in the lower part of that range in the bass and/or mid-bass regions, where lots of energy is typically required. As you'll see in these measurements the ST-140 has significant issues dealing with 4 ohm impedances.
Also, the ST-140's input impedance is spec'd at 24.3K. More likely than not the two output jacks provided by your preamp for each channel are driven by the same output stage, with the two jacks simply jumpered together just inside the rear panel (as opposed to each jack being driven by a separate output stage). If so, and if you were to drive two amplifier input channels from the two output jacks the preamp provides for each channel, the preamp's output stage would see a load impedance of 24.3/2 = about 12K. That will be too low a value for some preamps to drive with optimal sonic results, particularly if the preamp is tube-based.
Regards,
-- Al
Also, the ST-140's input impedance is spec'd at 24.3K. More likely than not the two output jacks provided by your preamp for each channel are driven by the same output stage, with the two jacks simply jumpered together just inside the rear panel (as opposed to each jack being driven by a separate output stage). If so, and if you were to drive two amplifier input channels from the two output jacks the preamp provides for each channel, the preamp's output stage would see a load impedance of 24.3/2 = about 12K. That will be too low a value for some preamps to drive with optimal sonic results, particularly if the preamp is tube-based.
Regards,
-- Al