I've never understood the concept of having that much music on a portable DAP. To me, its exactly that. Portable, and I think I'd be hard pressed to find someone who was constantly moving around to the point that they'd viably be able to listen to 3k+ songs.
If you want quality, and THINK you might be in this for the long haul, I would rerip all of your stuff to lossless, archive it on an external hard drive maybe, and convert down to different codecs, etc for your DAP.
To me, I really don't understand wanting to have premium quality sound, paying for hardware, and then refusing to use *at least* 320kbps. IMO, It's kind of like buying a sports car and then refusing to go more than 40mph. You've paid the money for the phones, expressed an interest in getting the best sound that you can(by buying them..to some degree) and then refused to utilized them to their full potential.
I really don't mean to come across the wrong way, I just dont understand the logic behind the constraints that you've given yourself in wanting to upgrade.