My guess is that the Bel Canto DAC, which is reputed if anything to be a little on the smooth side, combined with the Golden Cross(also reputed to be on the laid back side) may be in large part responsible softening some detail. I would think replacing just the Cardas with the DH Labs would bring a lot more detail back to your system. If that works but goes too far in the direction of brightness then something like the Bear Labs might do the trick. I'd also highly recommend Acoustic Zen's Silver Reference interconnect, which is very full and detailed but not at all bright(at least in my system).
In my experience changing even one interconnect can make a dramatic change in the sound of a system, which I would have thought you would have already found out with all the different combinations you seem to have tried. If this doesn't work I'd look at trying another DAC and/or speaker cables to see if either of these can get you what you want.
I'm not sure about having to match cables from the same manufacturer. I'd think its more important first to have cables that work successfully with the output/input impedance characteristics of the individual components in your system. Hope this helps and best of luck.
Tim
In my experience changing even one interconnect can make a dramatic change in the sound of a system, which I would have thought you would have already found out with all the different combinations you seem to have tried. If this doesn't work I'd look at trying another DAC and/or speaker cables to see if either of these can get you what you want.
I'm not sure about having to match cables from the same manufacturer. I'd think its more important first to have cables that work successfully with the output/input impedance characteristics of the individual components in your system. Hope this helps and best of luck.
Tim