yeah, I spoke with todd on the phone about this setup and indeed I think he spoke about resistors, but I am not 100% sure about this. English is not my first language so I may have overlooked this detail. I think he has talked about a 10 ohm resistor or something. it will be the first time I plug a headphone on speaker terminals, so yes I am a newbee at this. but the hifiman sound signature is my favorite. I have tried audeze lcd2 rev 2 and did not like them that much. my favorite part of the sound spectrum of an headphone is the midrange presentation. I have an hifiman he 500. it's my favorite headphone. a lot of people here have praised the he 6 midrange presentation as very good. that is why I want them. and I want to make sure they have plenty of power behind them at my first try. I am on a quest for my perfect headphone and I am realising that it is indeed a long journey. but I am getting real close. with the hifiman he 500, I have truly made a giant step in the right direction where my ideal sound lies.
If you are not sure, you can get a he adapter from hifiman. you will need some speaker cables, but it is a safe and relatively cheap way to go while you explore this. i use one and the sound is just fine, but you need to have some load on the amp i think. the experts can weigh in here