I have been very pleased with my Silver Dragon cable. It is clearly better than the stock cable. I can't tell to what extent this is because it is balanced and the stock cable is SE, because it is better made, or because it is heavier guage. I suspect all three. Also, I found Drew very pleasant to deal with, and his estimate of how long the cable would take was accurate.
I can't offer a comparison of Silver Dragon cables with APS 800 cables. However, I was able, at a local meet in DC, to compare my HD 800, with a Silver Dragon cable, against an HD 800 with the $1,400 Stefan Audio Voice cable and an HD 800 with a Blue Dragon cable. This is reported in a thread in the High-End forum on balanced 800's. The cables were all balanced. I tested the pair of headphones on my system and then on the system of the owner of the other respective headphone. I used several CDs (actually SACDs) that I am familiar with, with classical, jazz, and rock.
The test of the two Dragon cables was particularlly easy in that the owner of the cable had a Singlepower amp with two balanced outputs, so that it was just a matter of taking one headphone off and putting the other on. I did not hear any differences in the two cables, even though one is silver and the other copper.
I also did not hear any difference between my cable and the Voice, which is copper. 4N6, the Voice's owner, did hear some differences and found that the Voice provided a little more detail, but the differences were minor.
If either of the two copper cables had made a significant improvement, I would have been quite interested in acquiring it, and so my wallet was relieved by the test.
YMMV.