When it comes to impedance, JWM is correct. He's also correct regarding the Speltz autoformers. Some may argue the point but they definitely defeat all the advantages of OTL. Duh, he's also correct when he recommends "tubes somewhere in the chain." He and I both agree, start with tubes in the linestage.
Pani, ATC claims 8 Ohm and "flat impedance curve" so I don't see a problem. At 85db, the SCM40 isn't all that efficient but I'm guessing the M60 monos would do the job. My MA-1's had so much gain driving my 6 Ohm, 90db speakers, I ended up removing one of the 6SN7's(at Ralph's recommendation) to give me finer adjustment at the lower end of the MP-1's volume control.
Pani, ATC claims 8 Ohm and "flat impedance curve" so I don't see a problem. At 85db, the SCM40 isn't all that efficient but I'm guessing the M60 monos would do the job. My MA-1's had so much gain driving my 6 Ohm, 90db speakers, I ended up removing one of the 6SN7's(at Ralph's recommendation) to give me finer adjustment at the lower end of the MP-1's volume control.