Hello Dominick,
Congrats on getting the M80s. First, let me say that your Luxman is nearing or at the end of its useful life. That said, Luxman amps back in the old days were well designed and yours should drive a 4-ohm load without difficulty. Do you still have the specs on the Luxman? Does it have power output ratings (RMS) into 4-ohm loads? Older stereo amplifiers were quite robust and could drive 4-ohm loads easily.
The M80s should not be doing what you're hearing. I suspect it's sound card related or perhaps the Luxman has aged and its output section is having trouble with the 4-ohm load of the M80s.
By the way, despite Emotiva's claims, some of their amplifiers have also shut down driving M80s. Axiom M80 owners have documented the Emotiva problems on this forum.
The brands of AV receivers that have no trouble driving the M80s include Denon, Harman/Kardon, Sherwood Newcastle, Rotel, Outlaw Audio and NAD. Even entry-level models of these brands will handle the 4-ohm M80s.
Regards,
