If your upper limit's a little flexible, you might consider the Sennheiser HD558, which usually retails around $150; I've had mine for some months, and it is my considered opinion that they're the best headphone to be had under $300.
In particular, they make the MDR-7506 look bloated in the lows and weak in the mids and highs; I once compared the two headphones with a Karajan/Berlin Philharmonic recording of Tchaikovsky's overture '1812', and it wasn't even a contest -- the 7506 rendered the final crescendo so badly, with the cannon fire so thoroughly overwhelming the entire rest of the orchestra, that I couldn't even stand to listen to all of it.
As with almost all Sennheiser products, the HD558s are as neutral as possible (modulo the odd bit of foam, so I gather), and that's not for everyone; I listen mostly to music from the common practice era, so neutrality suits me well, but more modern music probably wants a more forgiving headphone -- listen to new pop masters in a set of "warts and all" cans, and you're going to hear a lot of warts. In any case, if you can make the opportunity to try out the HD558s before you make your choice, I think it's well worth your while so to do.
Any recs on a headphone that doesn't destroy modern music? I listen to prog rock/metal/classical/techno and I think I'm just looking for a nice soundstage and 'fun' headphone. I listen to some of this stuff on the HD280 and it sounds really flat.
I tried the HD700 in the store and it was unbelievable. But I'm not paying that much for headphones.
I'd love to help, but the only personal experience I have is with Sennheisers, which even their detractors concede are the most neutral line on the market. Since neutrality is paramount among my requirements for headphones, that suits me just fine, but it's left me without sufficient experience to serve as basis for the sort of recommendation you seek.
In particular, they make the MDR-7506 look bloated in the lows and weak in the mids and highs; I once compared the two headphones with a Karajan/Berlin Philharmonic recording of Tchaikovsky's overture '1812', and it wasn't even a contest -- the 7506 rendered the final crescendo so badly, with the cannon fire so thoroughly overwhelming the entire rest of the orchestra, that I couldn't even stand to listen to all of it.
As with almost all Sennheiser products, the HD558s are as neutral as possible (modulo the odd bit of foam, so I gather), and that's not for everyone; I listen mostly to music from the common practice era, so neutrality suits me well, but more modern music probably wants a more forgiving headphone -- listen to new pop masters in a set of "warts and all" cans, and you're going to hear a lot of warts. In any case, if you can make the opportunity to try out the HD558s before you make your choice, I think it's well worth your while so to do.