Which IC is more important?

Well I too am a believer that you start with the source but my cable experiences paint a much different picture. I have learned that there are two links in my system where cables make the biggest difference: line stage to amp and tonearm cable to phono stage.

I have tried so many cables (NBS, Transparent, Cardas, AQ, Straightwire, SilverAudio, Magnan) and I can move around different cables in the system to listen for differences. The link between the line and amp is always the biggest difference. This was more about preserving the ambience and bloom of the system (Linn TT, Pioneer PD65, ARC DAC3/PH2/LS5/VT130 and Maggie 3.3. Some cables in this link retained the magic and others completely lost it. I could swap cables between phono stage and line or DAC and line and here some changes in resolution or tonal balance, but it was subtle...the link from line to amp was not subtle at all.

I worked so hard to try to hear differences with speaker cables and yet, the changes were again so mininal. The only other area of significance was the tonearm cable. Here resolution was very apparent. The SilverAudio was miles ahead of the ARC or Straightwire in terms of information retrieval.

So for me it has not been a matter of the better cables at the front of the chain. And this surprised me. But I have learned that each link tends to be affected by cable changes differently than the other links. Sometimes resolution, or tonal balance or ambience, etc. For me, the NBS Statement works by far the best in the line to amp link. But the Cardas Golden Cross worked well too but perhaps a little too warm and rich in the midrange. But it took the NBS to bring on another level of resolution and retain the magical ambience of the system. Swapping source cables to the line stage had minimal effect on this.

Your experiences may end up totally different. Always try before you buy!

"The upstream cable is always more critical because it affects everything downstream." No! It really comes down to how each component integrates with the rest of the system. And some links in the chain are far more critical than others. All this said, in my own experience, I can put a cheapo $30 Canare or Belden XLR 1m cable between my phono (ARC PH2) and line stages (ARC LS5II) and a multi-thousand$ NBS Statement XLR cable between my line stage and amp (ARC VT130) and this works incredibly well. If I reverse these cables, all of the magical ambience and resolution brought on by the NBS is GONE! The line-to-amp link is just a lot more critical in the context of my system. It's that simple. Whatever science or theory or salesmen or magazine reviewers may tell me, my ears tell me a different story to what I would have expected. And putting another expensive cable in the phono-to-line link makes a very minute difference....so I don't bother with one in this link. Of course I would love such a cable to bring on another level of performance here, but it just didn't happen. Was I disappointed? A little as I wanted more....and yet I saved a lot of $$ in the process. Maybe it's the output/input impedances between the connecting components, the location of the components in the room, etc., I don't know. But I don't make any blanket statements as to what is "best" or "always". You just have to borrow a few different brands, perhaps many pairs of each, start with one brand throughout and then swap a link at a time and see what cables works well in each link. Some cheapo cables just might outperform very expensive ones or at least be so darn close that you recognize the value. Don't be afraid to put a $30 cable in between $10k of components. And don't be afraid to put a very expensive cable between less expensive components. The prices on some of these products often has nothing to do with their musical virtues so try all combinations you can. And don't be concerned about staying with one brand of cable. That's another misnomer. Hope this all helps.