I'm very happy with my QB-9 but I also think upgrading that piece could be the "last" thing I do to my system. I'm super happy with my amp (AX-5 Twenty) and speakers (modded Thiel 2.4). The QX-8 is appealing because I could simultaneously connect my Roon-dedicated NUC and a PC for watching concert videos. With the QB-9 I need to manually change which input device is connected.
I previously upgraded my AX-7 to AX-7e and QB-9 to QB-9 DSD. In both cases, the SQ was noticeably improved and at a fair price. I need to learn more but I might just stick with the more cost-effective solution of upgrading the QB-9 despite its single input (this was never an issue until I switched to the Roon NUC which cannot do videos).
I previously upgraded my AX-7 to AX-7e and QB-9 to QB-9 DSD. In both cases, the SQ was noticeably improved and at a fair price. I need to learn more but I might just stick with the more cost-effective solution of upgrading the QB-9 despite its single input (this was never an issue until I switched to the Roon NUC which cannot do videos).