As you both (Wenger and Andrewg) acknowledge the important contribution both source and cables make towards SQ, the debate is really about how one apportions expenditure between source (and other black boxes in the chain) and cables, which I eluded to in my earlier post.
There have always been very expensive cables you could spend your money on but most of these in the past have not provided VFM, particularly in the context of a Naim system. It does seem to me however in recent times some cable manufacturers have upped their game with regard to providing undoubtedly expensive cables, but cables that work well with Naim systems. Chord, TQ and of course Naim themselves with SuperLumina spring to mind. If you are prepared to do the home demos, it is possible to get a great bang for your buck with expenditure on cables.
Sources and other black boxes have also stepped up too with the advent of wonderful streamers and power supplies and amps with DR technology. Things have moved on significantly.
The only way to assess in your own mind what the right balance of expenditure is between source (and power supplies/amplification) and cables for you in your system in your own listening environment is to.......well you know what comes next. Wenger is certainly putting in the leg work and appears to getting great results from TQ cables, although we still await the final outcome. If he concludes it is worth spending more on cables than a source (or pre amp) upgrade then that is the right answer for him. If we were only able to open our minds and try for ourselves who knows it may be the right answer for others too. Of course to conclude after home demos that spending more on a source delivers better SQ than expensive cables, this would be a perfectly understandable position.
No one can know the answer until they actually sit down and listen too 'better' boxes and cables. Expensive cables often get a bad press, mainly due to their poor image of the past, perceived poor VFM, snake oil and all that stuff. After all, what difference can a bit of over-priced wire really make? Well quite a lot in my experience, but only if you are prepared to put in the leg work and properly evaluate them. I'm afraid guessing at the maths of black box and cable contiributions to SQ is no substitute for a home demo.