I loaded my Mac book pro into its case and headed for the dealer, he sent me an e-mail that the 660's had arrived. We plugged them in using the adapter cable as they come with the 1/4" Stereo phone plug. I listened to a bunch of selections I have on the hard drive. They are definitely an improvement over the 650's with an over all more balanced sound with a much better top two octaves. I think the bass is a touch cleaner, dryer for sure. They are not as efficient as my 598's so they wouldn't be a good choice for replacements for the computer. But driven by my 2505 or C-34 head phone jacks would be just great, I imagine. They are not Stax or Signet electrostatics however. But for the price they are outstanding. I wish they had been available all those years ago when I found the 800's just to strident. But then i'd never had been forced to buy the signets, and then move on to the Stax electrostatics. I even pulled out my Stax S 40's, I haven't used in years. Theres a contrast in sound. Which is better, the 660 or the SR 40? That will take further study.
I know the 660's aren't cheap but if you want to jump in with both feet to experience headphone listening a 660 just might make you a avid user for life.