I also agree on the ER-4S scaling with better amps. It's not a huge difference, but it's clearly audible.
i thought this too and said the same thing. Just read my posts in this thread. I described a well amp'd er4s as more open and spacious with more distinction and effortlessness. But the truth is, once i did a fair conparison via a/b, i have to be truthful and say i was "hearing things".
I won't say there aren't improvements with higher priced amps. I can't say that without trying them all. However, i will say price isn't everything. Take the c5 with a dedicated dac for example. More than powerful enough to drive the er4s and then some. Has incredible specs all around. Measures amazingly well, just superb. Incredibly low noise floor, non existent thd levels, perfect channel balance. Incredible power rail system for amazing all around performance.
It sounds the same as the fuze.
That's a tough sell for most people, but in a direct a/b test i hear no discernable difference. I can't even "feel" a difference in the sound at all. Now i'll list all my audio background if you want to hear it, but i'll just say i have very very good hearing. I can hear very minute differences even my fellow audio engineers miss. The point being, they hear a difference and i don't. Why? I think because they "think" they hear a difference they do. The mind is a powerful tricky thing.
So what about a $2000 amp? Well, first show me a spec that is better than the c5. Is the c5 perfect? Maybe not, but every spec is good enough that any audiophile into audibilty of things like thd, etc. will tell you the specs are well beyond what you can hear as an improvement. For instance, it is widely agreed that somewhere above say .5% to 1% of distortion is where it becomes audible. O.k., you say, but you can hear .25% distortion... The c5 has .0009% thd! That's well beyond any audible difference. So i don't believe a $2000 amp can audibly improve on that. Same goes for the other specs. In fact a lot of expensive amps are tube amps, and they have very audible distortion. But a lot of people find the effect pleasing. So is that a bad thing? Not if you're into that. But is it better? I'd say technically no, but to each his own. Music is art, but i believe the perfect reproduction of music is very much science.
My point is, there are laws of diminishing audible returns, i think pricey amps can be neutral and simply have great specs and sound great. But they can also color the sound for good or bad. They have beautiful designs. They're hand made, etc., etc. but in the end it is the sound that matters to me.
If you give the er4s sufficient power and good clean signal with a flat response, they sound great. The fuze dies this as well as the ipod as well as an apogee interface as well as a $1800 denon receiver. And i think everyone should prove to themselves whether they can hear a difference or not with a double blind test. And what is the difference you hear if any?
I'm sure i'll get a lot of crap for this, but again, this is coming from someone who truly thought there was an improvement with a nice amp. If you want to send me more material i'd be glad to do even further testing. Maybe i'll even pass around my a/b switch...