I find the sound of the ESP-950 to be similar to the HD650 except without the veil. Definitely mid-centric. I would not call them bright, but rolled off in the treble and bass while still being revealing of bad recordings. In my experience, all electrostatics headphones lack weight in the bass and sound "ethereal." There's tons of detail but no "slam" at any volume. I'm starting to just accept this. What do you mean by smearing congestion? I don't hear it, but I also don't have trained ears. The ESP-950s are nowhere near as nasal as the Shure SE535s, if that's what you mean, but I prefer the SE535s in some respects for being less resolving of flaws and having tons of bass. Someone suggested that the cheap amp can muddy things up at very high volumes, but I've yet to experience this. I have the ESP-950s and HE-4XX, which some people say sound like cheaper HE-560s? They're not that different, but the HE4XX sounds really plasticky and less effortless. But it's quite a performer. I far prefer the Koss for classical.