I've had both, I think they are quite diffrent. I really like Quattro Fil, it's just that in all it's glory it sounds a bit sterile to me. More information gets through the Quattro Fil compared to the Siltech, or just about any other cable, it's just that it can sound sort of thin at times. Siltech was more forgiving offering a warmer sound. I ended up prefering the Quattro Fil to the Siltech. I had the Coincident too and I didn't think it was that good, probably worth the price but definatly not that good. I personally think Acoustic Zen Silver reference is much better than any of these, that along with Satori Speaker cable is my new refrence, and I think for now my cable search is over.
