So it sounds like while I could use my speaker amp for my soon-to-arrive HE-1000s, I shouldn't. That's fine. I have several amps, and I conclude from posts in the HE-1000 Beta User Impression Thread that it is relatively easy to drive (yet scales up from perfection to nirvana as the amp scales up from powerful to Just Right!!)
I am able and willing to purchase an amp (and DAC too if necessary) for my HE-1000s. Ideally, it would also complement my collection of 13 Grado headphones, so I am looking at amps good for both. Candidates to date include the MAD Ear HD+ and the Schitt Lyr 2.
My Sennheiser HD 800s are admirably served by my Sennheiser HDVD 800 amp. However, it does NOT sound good with my Grados. The HDVD 800 impedance is 43 ohms; the Grado (and HiFiMAN HE-1000 impedance is 32 or 35 +/- 5 ohms, respectively. The HD 800 impedance is 300 - 600 ohms, depending on frequency. So the HDVD 800 amp, while Great for the HD 800 headphones, has an audible disadvantage when used with the 32 ohm Grados, and hence I assume, with the 35 ohm HE-1000s.
Any further amp suggestions? HiFiMAN EF-6????