There's no such thing as purity of sound. If you like hearing it the way it was intended you wouldn't be listening to headphones anyway. There's nothing wrong with listening to music on headphones instead of speakers, in a living room instead of a sound studio, with a DSP instead of straight, or with a room correction DSP for that matter. When a signal hits a transducer, all bets are off. You aren't talking about purity of sound or perfect fidelity any more. You've entered the natural world of compromises and optimization. You should do what you can to make it sound as good to your ears as possible. And it's fine for other people to do the same. Experiment and see what works best. I have a multichannel speaker system with a variety of DSPs to choose from. I can tell you exactly what the hall ambience DSP is good for... Arturo Toscanini recorded with the NBC Symphony Orchestra in Studio 8H. The studio was large by radio standards, but it was much too small for a symphony orchestra to record in. The performances in these recordings are brilliant, but the mono sound is boxy, dry and harsh to the point that it is difficult to listen to them. Playing these recordings though a multichannel hall ambience solves all of the problems... The sound field is surround instead of just mono, the sound is opened up and allowed to bloom properly, not boxy, and the hall reflections add a natural sounding acoustic to notoriously dry recordings. The difference between playing these recordings "as they were intended" and "enhanced" is not at all subtle, and even the most dogmatic audiophile would agree that using the DSP in this case is a vast improvement. It doesn't just alter the sound, it improves the recording itself and makes it sound more natural. DSPs are tools that can be used well or used poorly. A hammer can be used to build a house, and it can be used to bash someone's brains in. The hammer itself isn't bad. It's the same with DSPs. In a perfect world, all recordings would be perfect... they would all be multichannel, they would all have perfect balances for your particular living room,.. they would all be recorded in perfect venues. But we don't live in a perfect world, so dogmatic approaches to "signal purity" aren't smart. It's better to have a good selection of tools and know how to apply them well.