Allow me to rephrase. In my case I own the 2270, and while technically, yes, I can put any headphone I want in it, many of them lack great synergy with the Marantz. While it was only temporary, running my D7000 through the 2270 was not ideal in anyway. Yes, it sounded cool, and could rock my skull into oblivion if I so desired, but in general, it was VERY bassy, and bass dominated. My volume knob never exceeded 9:00 o'clock, and I would say the 2270 was too strong for it as a whole. In fact, I would even go as far to say that from a "serious" standpoint, it was a very flawed setup.
The HE-6 on the other hand, really benefits from all the power that 2270 can throw it. Instantly, I felt a much better synergy between the two. Outside of the HE-500, what other headphones really like vintage receivers? Yes, I could buy the HD-800, T1, or LCD Rev 2/3, but wouldn't those be much better off with a WA22, or the Decware CSP-2?