The best amps i have for my HD800 are the Rudistor RPX-33 mkII I bought used last year. And the Singlepower MPX3 I also bought last year, used.
The next in line is the headphone out of my Bryston BP-26 preamp.
I also have a TADAC DAC with headphone out, and just sold a LittleDot mkIII headphone amp.
I bought a handmade (closeout sale, but i still paid a couple hundred bucks) HD800 headphone cable from i do not remember whom, and it is definitely a better cable than the stock one.
Hi Elizabeth - are you really a female? If so, wow, that's great - don't run in to many of the other persuasion in these circles. I wish my wife had greater interest in my passion. She's a musician and serious music lover, but equipment bores her. But she always complains when she listens to what she considers a bad sounding system. I've had many (too many) components over the years, and I always had a hard time getting her to listen to a new piece of gear or new tweak. She has a very sensitive ear, so I do like to get her opinion. She is remarkably consistent at identifying tube gear vs solid state. Without knowing which is which whenever she sat down to listen to a ss amp or preamp, she would leave the room within the first minute complaining that it sets her nerves on edge, and I could never convince her to stay longer. The only time she would stay longer and ask to listen to more music was with tube gear - not all tube gear, but only with tube gear (save for one SS piece: a vintage Nelson Pass design). She never knew if the component was SS or valve.
Being new to headphone mania - it seems like many headphone enthusiasts have multiple headphone amps. Why is that? I would think that once you decide which is your favorite, the others would just sit on the sidelines. Why not just sell them?
But I'm digressing.
Thanks for the information to all who have responded so far.