Hello. So I am currently using the Ultrasone Pro 2900 driven by an Aune X1s. Yesterday, I noticed that the 2900's sounded somewhat veiled when being used below a certain volume - though not to the point that the volume was too low for that to be the issue. I asked the guy I bought them from, if he knew what was going on, and indeed, he did. He told me, that even though the headphones aren't that powerhungry, they do sound a bit veiled or muffled if being by an amp that is not powerful enough. Could one say that these headphones need an engine (the amp) which provides a lot of torque, and not only horsepower? Because the Aune can drive the 2900's to unlistenable levels (horsepower), but if it does not provide enough power (torque) at low volumes, it's no good. Is the analogy above somewhat accurate? If so, what amp would you choose or recommend me on a 100-150$ budget?