Should I update Ayre QB9 dac

If you call Ayre, they will give you an honest answer. If I was in your place, I trust Ayre enough to go with whatever way they say is best.

I’ve heard both. Although, some say that the QB-9 DSD sounds better, personally I think the Codex sounds as good if not better especially with a few upgrades like the power cable. I own the Codex and I’m very happy with the performance. Like all Ayre components though, they sound the best fully balanced. Is your system single ended or balanced?  If your running a single ended system, I would also consider other DACs .  With the Codex, I noticed that balanced or not balanced makes a significant difference in SQ. Don't get me wrong the RCAs sound great, they don't compare to the balanced outputs.  

Thanks for the feedback. I am running in ballanced mode into a BAT pre. Ayre always stressed using xlrs.
I called Ayre customer service and they recommended getting the upgrade. They felt I should give it a try and I could always move up latter. Also easier to sell with upgrades.
Seems the new DACs are emphasing features rather than major upgrades in processing. I'm told USB only was the sore spot for Ayre with the QB9 and the new models change that.

I've heard both as well and actually prefer the QB-9 DSD to the Codex. I thought the older DAC sounded a bit more refined. One of these days I'll get around to comparing it to the new QX-5 Twenty, but I don't really need multiple digital inputs right now.

I liked the Codex with PCM, but DSD didn't sound very good through it. Not sure how the QB-9 DSD handles DSD, but maybe this is one reason people prefer it?