Incidentally, I asked Yannis for his views on the comparison between the SPD-4 and the 423.5 Phono Litz. This is what he wrote:

Regarding the comparison between the standard 423.5Phono-Litz and the SPD-4:

I consider the SPD-4 to be less “edgy” than the 423.5Phono Litz. Its balance is focussed more in the Mid-range rather than the upper frequencies. I think that both cables are quite analytical in both width and depth expanding the entire sound stage but the SPD-4 is “full” and well rounded. As I mentioned earlier, I would expect the SPD-4 to have very similar characteristics with the ones you observed with your version of the 423.5Phono-Litz. So after giving such a review on the 423.5Phono-Litz I am not sure what to expect from the SPD-4. Again, their price is not an indication of performance but a direct reflection of materials/parts and labour.

However, the SPD-4 “technically” has a superior construction adding variable conductor gauge between “send” and “return”, variable strand gauge within the same conductor for lower electro-mechanical resonance due to the elimination of strand multiplicity, and additional shielding features. As I have explained, the SPD-4 was developed to be a Hybrid design (and this would imply different characteristics). However, yours (and Andy's) versions are pure silver, so the result will be quite different than what it was initially designed for.

In other words the Hybrid SPD-4 would be a very musical and relaxed cable (with some added colours that make it more pleasing rather than offering a cold reproduction of the recording) as a result of the inclusion of copper and Mundorf silver/gold; but the Silver SPD-4 is likely to be faster and more analytical.

Also note that the SPD-4 uses dual shielding: a highly conductive copper and nickel coated fibre mesh which is placed between the inner insulation and the outer shield. The outer shield is a high density silver plated copper braid with 97% optical coverage (same as the one in your 423.5Phono-Litz).
Interesting... It should certainly make for an intriguing comparison!

Marco.