Higher Efficiency Speakers

@larryi ,
My Atma amps have no hum whatsoever. If you did have hum, perhaps you had grounding issue. In any case, I would have called Ralph to get to the bottom of the issue.
Bob

Terrific.  Absent noise issues, the M-60 is a great amp for almost any reasonable loudspeaker.  I was just concerned about the OP's situation because of his plans to utilize high efficiency speakers.  

Those Salk 3’s are beautiful, but also 88db - not the most efficient.

Don’t lose sight of Decware, either:
http://www.decware.com/newsite/HR1.html

Unless the speakers are up against the wall and your seating against the opposite wall (not ideal, both your seating and the speakers should be at least 2ft off the walls, use a sofa table or something to take up space if you want). 
 
Ideally wattage should double with the halting of impedance, so even though your amp is 60W into 8ohm, it is 45W into 4ohm (unless this is a typo), meaning if you use a 4ohm speaker, you are efficiently feeing it <25W if it were an 8ohm speaker. 
 
At 10ft away and wanting 100dB peaks, you would need 91dB or higher efficency. 
 
The Noesis 215RT would be excellent at <$7500 shipped, not sure if the looks are for you though. 
 
Salk also custom makes speakers, so you could go that route, it would just take a long time as they would have to find the suitable drivers, test that it would work well, fine tune it, etc.

Klipsch Heresy IIIs...a steal at around 1500 bucks new (look around), not sure anything comes close...built like a tank, unique slanted fat little things that sound beautiful, and 99db efficiency works with anything.