HPS:
Beyerdynamic DT-770 (250 ohm)
AudioTechnica M50x - Black version (38 ohm)
AMP:
Rolls-Bellari HA543 (with RCA & balanced XLR inputs)
DAC:
Insignia NS-HZ313
EQ:
Equalizer APO Configuration Editor (no Peace UI)
My sound source is the optical output of my Samsung TV. And most of the music I listen to is from YouTube videos, fed to my TV via HDMI from a laptop. It's probably not the ideal setup for most people. But it is quite affordable. And works pretty well.
The bit depth and sample rate that I use for the laptop's HDMI output to the TV is 24-bit/48 kHz btw. I chose this rate rather than the standard 16/41 for several reasons. First, it's the highest rate that my TV will accept via the laptop's HDMI connection. Second, it is the standard rate for video content. And third, it is the rate used by YouTube's Opus audio codec. It is also easily handled and converted to analog by my cheap Best Buy Insignia DAC (which only handles rates up to 96 kHz). In short, it keeps my audio as clean and pure as possible from the source to the amp.
If you're using audio content encoded at different or multiple sample rates or bit depths though, then this may not be as optimal an arrangement, because some rate conversions would likely be required. There are other software music player solutions though that can be used to keep the audio content at its native sample rate from the source to a DAC. Since I generally only listen to music on YouTube though, and am passing through an intermediate source device that's designed primarily for video (my Samsung TV), I think its better in my particular case to keep the content at the standard video rate of 24/48.
I chose the Bellari HA543 as my amp because it was one of the least expensive models I could find (made in the US) with both RCA and balanced XLR inputs. This allows me to use the amp with both standard consumer line level audio inputs, and also balanced pro audio line level inputs (such as from a mixer). Which is a handy feature to have, if you like to dabble at all in some music production. Or use a mixer for your EQ. It's not a super powerful amp. But it has enough power to drive both my lower impedance headphones, and the higher impedance 250-ohm DT-770's to more than adequate volumes, with no audible distortion.
I rarely use the M50x, btw. And mostly use just the DT-770 as my primary headphones, because its large velour pads are quite a bit more comfortable than the M50x's. Both HPs need some EQ though to tame a few peaks, and to smooth out some of the rough spots in their frequency response.
Prior to purchasing the above headphones, I used the AKG K553 Pro. (The version without the detachable cable.) Which I believe uses the same extended frequency titanium drivers as the K371. The AKG K553 is a much heftier, and potentially more durable (except for the pads) headphone than the K371 though. Designed for people with very large heads. So it's not the sort of headphone I'd recommend to just anyone. It has very large plush pads though, and almost no clamp. So it is a pretty comfortable headphone for longer term wear. Especially with a few modifications to the pads, on both the earcups and the headband. After about 5 years of heavy use though, the K553 just eventually wore out. And needed to be replaced with something new. So I thought I'd try something new, and got the DT-770 and M50x.