If you're producing music, then the 7506, srh840, ath-m40, and K240 studio will all be acceptable. These are all headphones that you often find in music production, and they are all driven very well out of even the most basic production equipment. Really, you will be happy with the sound of any of them.
The Sony 7506 is seen in many recording studios, despite the fact that Sony sold the PS3 the way they did (I don't see this as relevant to how the Sony headphones perform. Besides, Sony definitely got their comeuppance in that the PS3 lags way behind the Wii and 360, and that many of their sales are just people that are wanting to buy a Blu-ray player and end up deciding that the small price premium is worth it to upgrade to a playstation. Also, the Gran Turismo bungle cost them nicely, and it has met to rather underwhelming reviews. Many of the car blogs recommend this game as a "don't buy, it isn't a finished product even after such an extended development period"). Don't judge headphones by their price, judge them by their performance.
Overall, you'll find that, when you go to studios, they don't obsess over which particular headphone they are using, and which particular amp they're driving them out of. Let that tell you something.