Do you have recommendation?
whattodo
It is personal choice/taste/budget here, but as I've invested into the C9ii, my IEMs, cable to the IEMs, I'd be crazy not to optimize the IC but doesn't mean you have to do what I did so will give you a range, but don't expect the bargain IC to perform at the same level as TOTL.
But to me was still better than the stock IC (which FYI isn't bad, its just that you can improve with this change)
I've had and reviewed (and provided links earlier) to the 2 IC reviews I've done for the C9 and the C9ii
https://www.head-fi.org/threads/cay...ss-a-ab-portable-headamp.943135/post-16615751
and here
https://www.head-fi.org/threads/cay...imbre-anode-nfb-pre-line.973711/post-18444904
I've had custom IC's made from Plussound and they are still in my rotation but latetly I've been using the Eletech Euclid IC more.
I've also ordered a Eletech Sonnet of Adam 6 wire (grounded) IC for the C9ii as I think this will help remove some background static as well as improve the stage.
Bargain Basement
GUCraftsman Silver IC
Though small gauge wire its a true 6n OCC silver, not a SPC (which I personally don't care for) or lesser quality silver I've found from some other lower cost IC's
Available on Amazon, today's price is $36
I've also had GREAT experience with the Plussound X8 IC's (and price can vary depending on what wire type you choose - Range is $199 to $1300)
https://www.plussoundaudio.com/cust...ries-Custom-Cable-for-Interconnect-p250248594
Really having great experience with Eletech's IC's
https://elementechnology.com/collections/accessories/products/proadapt-series-interconnects?variant=39308592283747
Again dependent on the wire you choose, Aristotle IC sounds to me much better than the stock Cayin and bonus its grounded, The Euclid was much better IMO than the Aristotle, the Sonnet of Adam did what I was looking for - The range is going to be from about $249 -$800
Would recommend at min the grounded versions.
There are also IC's from PW Audio, and other cable makers which I've seen IC's go for as high as $2000+
I have borrowed and tried many of them, but I've had great results with the ones mentioned above, especially the Euclid from Eletech and just keep coming back to these mentioned above as recommendations
Hope this helps, and the above is IMO, and YMMV