Another thing worth mentioning, the 99 Classic is being re-released in collaboration with Massdrop, called the 99 Noir, and the first drop called $200 which seems like a very good price. Don't know when it will go live again. It should share the same tuning as the 99 Classic. I haven't heard the 99C but I have heard the new pads really mess with the sound. Just about every major headphone reviewer said the bass is too much. Yet others on forums say it's not that bad. So I don't know. But I too find the H6 balanced pretty nicely and they're a great listen, especially with improved sources. They too are a little bassy, but mostly lower bass (I find it to be quite present on bass heavy tracks).
Actually listening to them right now, Under Pressure is playing. John Deacon's bass line sounds nice, tight and clean