I'm enjoying great audio with the Ayre QB-9 into an AX-7e running balanced with Cardas Clear cabling. But of course that's with USB in asynchronous mode, not compatible with your logitech transporter. It's rumored that the next Ayre DAC may support S/PDIF or AES/EBU input as an additional option.
Barring those, I recently heard a system with Antelope Zodiac Gold running in balanced mode that was also incredible, IMO. Good luck in your auditioning.