Best Headphones in $500 range for Leben 300X

I have not heard the Leben, so can't say what headphone will work best. I own HD650s and have listened to the AKG K701 at Head-fi meets. I have never been impressed by the K701. They tend to sound quite analytical, tend toward sibilance, and are relatively difficult to drive. They enjoyed a FOTM status a few years ago on Head-fi but no one over there who regularly attends headphone meets owns them. The HD650s, when properly driven, are a much better headphone. They are enjoyable, but have a slightly laid back presentation. However, my favorite headphone by far has been the JVC Victor DX1000. I stumbled upon a used pair for $550 about two years ago and now use them exclusively. They sound absolutely wonderful with any tube-based amplifier. In many ways, they are similar to the HD650s but just better them in every way. There is a very long thread on Head-fi about the DX1000s, which I recommend you take a look at. You can buy the European version new for about $650 from computer universe, a German online retailer. Many people regard the DX1000s as the "poor man's" Sony R10, a legendary headphone that cost $3,000 but are now out of production. Finally, avoid the K1000s. They are uncomfortable and out of production, so impossible to service.

I would check them out for yourself. You can buy the K702's right now for $248 at BH Photo Video. That's the only way you're going to find out. They are all good headphones, and the K702's are very very very well respected amongst serious headphone enthusiasts to this day. They're just as good as Senns, just different. I love both as well as Grado, mainly because of their differences. I wish I could own them all.

I would not recommend the JVC Victor DX1000. Not for any audio issues (they sound great!), but for the crappy plastic headband that will fall apart sooner or later, rendering the headphones useless. I speak from experience. I just replaced them with Audeze LCD-2.