You Should Try The Amp in Your M24...
3) On my big rig, my Sennheiser 580s sound mighty good. I have a cd transport + Monarchy DAC 24 that comes through astoundingly on my modest Perreux SXH1 headphone amp. The amazing thing is that with my Hornet and Denons, I am just as happy.
4) My next step is to use my Denons in my big rig, and then after that upgrade the amp to: Ray Samuels HR-2 or XP-7 or possibly the Rudistor RPX-33.