I bought a DAC about a month ago (FiiO K7BT Balanced HiFi DAC Bluetooth Headphone Amplifier) and put it through some work with many different musical styles and headphones. I hated it. I kept reading that the volume is logarithmic but all I could tell is that it only became useful around the 60-70% turn of the knob. And even then it wasn't driving any of my headphones, everything sounded flat. I connected it to my computer to test that part of it out and even then it was weak. it felt like I could put dubstep on and it would sound like a cardboard box.

Probably there's a case to be made that if I had let it burn in it would have gotten better but ~$300 is a lot for a maybe and a real good way to lie to yourself that it sounds better. It also did not help that it turns out my hires audio player does not output via the USB port so it was a headphone cable connected to the unit. Really good way to screw up sound when there are two volume dials to keep in mind.