What is the next step up from the ATH-M50 for closed cans that have a bit wider soundstage yet maintain the great punchy bass and clarity without getting fatigue? Looking to use iPad as my source not really interested in anything I'd have to amp. Does this exist or should I stick with getting the ATH-m50?
The logical step would be to an Ultrasone. The problem is that the model I would recommend (Pro 750) needs an amp--at least out of an iPhone 4. The leaves the HiFi 780, which is a bit more efficient.
Another option is the Shure SRH 940, but I have done an A/B comparison between it and the M50 about sound stage. The Shure SRH 940 is in the "it will work but it's close" category with the iPhone 4.