Bob...Dan's response is spot on and your plan to take the Ref 75 to demo it with the Futuras is the right thing to do. If you can swing it, take your VX-5 as well to compare the two amps. My guess is you will find the Ref 75 will do quite nicely in areas of timbre, resolution, imaging and spatial cues but will have a tougher time with bass depth and more importantly articulation as well as macro dynamics. The VX-5 will probably beat the Ref 75 on those two dimensions but may underwhelm on the ARC's strengths. You can also see if your dealer has a more powerful ARC or other tube amp (but again the key here will not be power rating but current throughput - amperage - given the difficult load). You really want an amp that is stable into 2 ohms and probably the auto former on the Mac amps will give them the edge vs. other tube amps. More likely though will be the need for a SS amp that keeps on doubling power as impedance is halved and is stable into a 2 ohm load. Perhaps the dealer will have some other options for you to consider (maybe try out a Class A SS design as an example). Good luck and let us know how you make out.
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