In my opinion, Cardas cables are "warm" sounding, and not neutral. But they may offset some of the "brightness" of the ML's that you notice. Also, if you have a "brightness" situation, with the ML's, then it is probably best to stay away from silver, or silver-plated copper cables, and go with copper. I don't have any of the gear that you use, so I cannot make a specific recommendation that would be "known to work" in your application. There are many SF and ML users here, and I'm sure you'll hear from them. Good luck.
I would describe the cardas in my system as neutral to slightlyly warm. it should not make your components sound bright. If you are trying to tame a bit of the brightness in the SF stuff you might try playing with the driver tubes in the amps. The sovtek 6922s are a bit on the cold/dry side of neutral.
I'd give Nordost Quatrofil IC's a shot, if you can afford them. They work very well if you can spare the cash. These cables are fast, accurate, and very detailed. They are pretty neutral. I have had a SF3SE preamp (still have it, going to sell it soon), and the QF worked very well with it.
I own ML Requests and cable matching is important. I used to own SF gear, SFD-1 MII, Line-1, SFM160 amps. I got my best tweaks trying different tubes. I now own Krell gear and use Pure Note cables. As other posters say, Cardas is warm.
Cardas Neutral Reference is not as warm as Golden Reference. It retains the nice Cardas midrange without the bass bloat of GR. I think you might like it. I've tried lots of ICs recently and keep coming back to NR because of its well-balanced overall tonality. In your system, I would definitely stay away from anything silver. I think it would be too edgy.
I'll throw my usual spanner in the works by opining that I don't find my Cardas Cross cables to be 'warm' despite the conventional wisdom reputation associated with the brand (they're actually brighter- and faster-sounding than my Harmonic Tech Pro-Silways), and also that I've never heard Martin-Logans to sound bright in and of themselves (they've usually sounded a little laid-back through the presence range and somewhat rolled in the top octave). You don't state your specific components (other than the speaker cables) or speakers involved, so I'll hazard a guess and say that the impedance and capacitance issues inherent to 'stats *may* be combining with your power amp and speaker cables as a network to create the problem - it's been known to happen. But the other humongous issue with dipole panels is, of course, in-room placement, the effects of which can vary wildly, depending on just about everything. (I do applaud your desire to aim for neutrality as much as you can.)