i figured since i went off maybe i could help some people here. since the device is in fact bus powered you can make a good improvement depending how much noise you have. probably a lot like most pc's. i like ifi's stuff but cannot recommend it due to their often untimely demise. so, what you can do. i will mention everywhere with the best prices on what you will need. there is no assembly it is plug and play. first go to abt and get the aqdioquest jitterbug and dragon tail. this will go into the usb port on your computer. try to use a usb port with nothing else on that controller. then go to cdw and get a startech usb hub with a type-a usb input. now go to music direct and get a .75 or 1.5 meter cardas clear usb cable. this will go from the jitter bug to the startech hubs input. now you will need a linear power supply to power the startech hub. either go to mouser and get one or better find an old radioshack regulated universal psu. if you do that set it at 4.5 volts. do not use any of the other ports on the hub. you will need to get a psu with the right size plug for the hub or correct adaptaplug if you go with the radioshack. now go back to musicdirect and depending on the sound signature of your system either get a cardas clear usb cable or an audioquest carbon in the length you need to reach your dac from the hub. i would try to suspend the hub so it is not on the ground or a table. otherwise put it on a cork drink coaster from walmart or a piece of foam rubber. plug the psu directly into a good surge strip or ups. i recommend an isobar from tripp lite. depending on how much noise you have this should make a subtle to a large improvement. The downside is depending on how long cables you need this is going to cost between $300 and $650. similar to what it would cost using the ifi equivalent but much less likely to quit working. if you have a lot of noise which you probably do this dac is in fact eating it and is is badly affecting your sound. so this should be a worthwhile investment. it is bs that they said originally that it was non bus powered. in that case you could forgo this additional investment.i would also put the codex on it's side and use the vibration isolation blocks i mentioned elsewhere available at lowes. however if you are not using balanced headphones or balanced outs in the rear you are not getting nearly what the codex is capable of anyways. if you are strictly using se this is not really worth the investment. with these improvements the codex easily beats many dacs costing 4-5X it's price but not all of them. of course also use good audio or headphone cables of your choosing. i am just fed up with ayre as a company. it remains with these improvements the codex punches well above it's price point. it still has quirks and they do not care. if you are stuck with it and have yet to take these steps it will probably be very worthwhile to you. the thing is now it is not $1,700 it is at least $2,000. still, you will be hard pressed to get anything anywhere near this price that performs as it does.
as for the qx-5 twenty to me it is too much money in retrospect because i use almost none of the additional features and simply use it as a dac. as i said it is better than the codex as a dac but not tremendously. you are mainly looking at a newer better chip. that is why i am considering the mytek manhattan 2. i will see how it stacks up to the qx-5 just as a dac. there of course will be other nice offerings with the 9038pro. if you cannot get out of the codex than these improvements may be worthwhile to you. i think with these improvements implemented it greatly closes the gap in sq between the codex and qx-5. not entirely though but solely as a dac i think there will be comparable offerings for less money. a big part of the ayre sound is their curve if you are keeping the codex for whatevewr reason, with these improvements it is still considered by myself to be at the higher end of the range of dacs. without all this it is of course still very good. you can most likely improve it quite a bit though. even with the quirks and lack of support it remains a top contender at it's price. even exceeding much more expensive offerings. i think you will also find there are less issues with ramped up usb power. so that is another plus of doing this. no, we should not have to do this and it is optional but unfortunately dacs like this tend to benefit from it a lot. plus it may well fix some of the issues. this just goes to more reason that i am mad at ayre as a company. they make good products but i am unhappy with their "policies". that is all.
i do wonder if they will abandon this, continue it's development or offer a different product. now that they have discontinued the qb-9. time will tell. i do find the codex to sound a little better than the qb-9 as is. that happens with the evolution of the chipset. thus greatly in part why the qx-5 is better imo. i do not really think it is their other "magic" and there is not a huge gap between them as dacs. there is most certainly some gap though. which i mostly attribute to the 9038pro which others may disagree on. with the qx-5 you are paying for much more than simply a dac. it is a network streaming device among other things. i just want a dac and feel i can obtain one for less money. not to mention i am just fed up with ayre on a personal level. for one thing as with the codex the qx-5 uses the same vastly outdated drivers. i just feel as if they don't really care. that is just my opinion though everyone else is certainly entitled to their own.
well, i hope i at least helped someone here with the suggested improvements.