Sennheiser HD 558 - Compatibility with amplifier sources

I have been using these open-back inexpensive reference headphones since [May 8, 2015] and the only part that has broken is the small plastic retention cog on the right and the outer headphone headrest housing-and this was due to an anger induced slamming of my headhones into my ikea desk, which ended up fairing worse than my trusty headset. Lightweight, strong body, with excellent acoustics due to the open design and with correct impedance and pre-EQ'ing just a bit they achieve really clean bass and crisp responsive(if even fatigue-inducing) highs. Even without proper drive-they can work great as portable headphones despite their lack of space-saving, but the lightweight and robust design means I don't have to worry about throwing them in my bag loose due to the opaque black filters which prevent contamination of the drivers even to smoke and tars.(I would know) I recently re-referenced them to get a more true response curve and my music has never sounded more like it does on my Klipsch Monitors on-ear, I don't know why I had never used this website to reference my headset(I used to do it based on preference and cross-referencing my music and other's based on my desktop monitors) Thank you for the guide, it made setting up Dolby Atmos for my headset and for another EQ program I intend to use for making music. Atmos with surround virtualization works excellent with these cheap open-backs because the sound does not create too much positive pressure even at high volumes. This also means a lot can be heard outside the headset, and some sounds may come in from outside-but this is my preference as I sit next to my partner and can hear them clearly at regular speaking levels if I am set to even 75% volume-but any higher and the escaping frequencies almost act like a noise-cancelling effect due to their escape from the rear side of the diaphragm. I am disappointed that these headphones are not true Sennheiser manufactured anymore and I implore anyone looking for these headphones to not get scalped as they were [$116.28
Condition: New - Brand New Factory Sealed!] on Scamazon and procured through a now deprecated and deleted seller by the name of [T.R.G] with a waveform in the logo and great reputation: [98% positive lifetime (23581 total ratings)] So I knew I would be getting genuine Sennheiser(even though this was of little concern in 2015...) Well, it may not be concise, but this is my review of these headphones, with complete positive biases, as I haven't dared put anything else over my ears, and trying to avoid putting things in my ears unless by necessity. I do miss my Shure IEM's though, gone with the wind-now..