I just happened across this thread, and I thought I would post my thoughts on this topic to it, (even though it was posted 8 years ago!), as I have fairly recently replaced my AU24 speaker cables, (bi-wired), with Nordost Valhalla speaker cables, (also bi-wired).
In my system, there is no doubt that the Valhallas are better than the AU24 cables. (The AU24 cables are very good cables, especially so for the money.) However, the transparency of the Valhallas is a bit better than the AU24 cables. The imaging and soundstaging seems a bit more precise using the Valhallas as well.
And I prefer the treble response of the Valhallas as well, even though I have heard that some people think that the Valhallas are a bit bright sounding. However, they work perfectly with my Lamm M2.1 monoblocks, which are just a tad dark sounding. So it matches up perfectly, IMHO.
And, I have also heard where some people think that the Valhallas are a bit lean in the mid-bass region. (I have noticed that there are an awful lot of people who take potshots at the Valhallas for some reason.) Anyway, the Valhallas seem to have tamed a bit of a mid-bass hump that my EgglestonWorks Andra II speakers seemed to have.
And yeah, I know some people say not to use cables as tone controls, but it seems to have worked very well in making my system sound much better than it has ever sounded before. So, to sum up, I am very, very happy with the sound of my system now, and I attribute some of this happiness to the Valhalla speaker cable upgrade. In fact, I consider myself done with my system as a whole, with the possible exception of an upgrade to my turntable.
My two cents worth anyway.
