is ayre qb-9 dac better than cx7e mp?

Not really familiar with the QB-9 however I can say without a doubt that the Wavelength Cosecant is superior to the C5xeMP which I used to own. My brother says it is no contest vs. the C7 which he also owns.

As you may or may not know, the QB9 uses the proprietary Wavelength asynchronous USB technology - but I've heard from several people that the Cosecant is far, far superior - although of course it does cost more.

If I were in the market for a digital source I wouldn't buy a CDP - I do believe that the technology is on its way out and service on transport, laser etc is likely to become difficult in the coming years.

Do not use any of those connections or USB DACs, sell your CD player and go discless. The sound will be far superior. A LINN DS unit is a much better sounding solution in one box, all controlled from an iPad and get rid of the CD player totally. Files would be sent via CAT5/6 from your PC or NAS and controlled in your listening chair with an iPad. Having any other connections (USB, SPDIF converters, etc.) are just mucking up the sound. Access all your music at better than CD quality once ripped with dbPoweramp into 24/96 or 24/192 FLAC or WAV files. The LINN Akurate DS will beat out CD players in excess of $10k.

With all due respect Audiofreak32 you are giving your own opinion. If there were one interface which was unquestionably better than all the others then that is all that would exist. There is by no means any kind of consensus here. Asynchronous USB DACs can sound great and do have some sonic advantages in a well-implemented design.

USB DACs can sound good (I have owned a very nice one), but when I listened to even the entry level LINN DS, it was no contest.

You are entitled to your own opinion. When I heard several Linn servers (they were peddling servers at 3 different price categories) in an all-Linn system at a show I was not tremendously impressed...