Then there were 2

@gakerty thank you for that reminder. I will check the specs on each amp.

@yogiboy Are you sure the M120 is not available? Did Mike tell you that? http://quicksilveraudio.com/products/mono-120/

90 days ago he was backordered with a backlog of customers. Not sure now, someone would need to ask him again for an update. I’ve had five different people unsolicited reach out asking me if I’d consider selling mine. Demand seems to be greater than supply at this time. They are worth the wait if you can.

a pair of mono 120 sold in 56 minutes the other day once posted on Audiogon. It was posted at 9:52pm and I got home at 10:50 and it was sold.

this is wierd my post did not "post"
lets try this again: Input Impedance
ARC 300K balancedRogue 200K (not specified)QS 100K single ended
ARC should be fine

There are 2 woofer in each cabinet. The woofers themselves are 90db. but with 2 in parallel it is higher but I dont have exact measurements of efficiency. speakers are 4 ohm.

@jimbones Tube amps do not double power as impedance is cut in half. That is why efficiency is a more useful spec than sensitivity when tube amps are involved. In this case, while sensitivity does increase, the efficiency remains the same. Since the total wattage of most any tube amp is lower into 4 ohms, I think you will find that you simply need more power.

I would also consider putting the woofers in series rather than parallel. They will act the same in the enclosure although you'll have to change your crossover a bit. But a tube amp will thank you as it will make more power, have wider bandwidth (particularly in the bass) and make less distortion.