Digital Cable Choice; how critical is it?

I don't know if Kubala makes digital (75 ohm) ICs, but if they do, stay with them (for RCA or BNC which is the 75 ohm I'm talking about). Otherwise, if you have AES/EBU connectors on your DAC and CD transport/player, those are always preferred over coax S/PDIF (RCA) or BNC (bayonet) IMO. Kubala has those I'm sure.

I don't know about that "CD direct" business. If your new preamp also has balanced inputs, I'd try it both ways. Betcha a new CD you like the XLR better ;--)
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Nsgarch, Toslink cable is now available with GLASS stranding. Glass Toslink made a HUGE improvement over the cheapo plastic Toslink. And this was in a relatively modest system!

Hi Mike -- That's not a surprise. Glass Toslink has almost twice the bandwidth as plastic. But its practical length is still only 5 meters, while AT&T ST cable can go up to 100 Km between repeaters (for those REALLY large listening rooms ;--)

The real issue with Toslink (for audio, that is) the poor quality of the little transceiver units. They cost about $5 wholesale (STs cost about $120 wholesale) and the quality of their signal output is affected by end-to-end reflections in the cables (another reason to use glass if you can) and transmission jitter (glass won't help with that.)

It can't ever beat AT&T, but whether a glass Toslink connection would outperform a high quality coax (RCA) or aes/ebu (XLR) I really don't know. It would be easy enough to try though, because today, almost all stuff that has Toslink has coax inputs/outputs well.

Here's a little Toslink history if you're interested:

http://www.audioholics.com/techtips/audioprinciples/interconnects/toslink.php
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Barrelchief, digital cable sonic difference = placebo effect = no measurable difference on recorded waveforms downstream of your dac. But they do look cool!

Oh forgot something I thought might be useful. Signal recording and analysis tools are getting reasonable in cost, very powerful and somewhat user friendly, certainly user friendly enough for a lot of serious audiophiles. For around $3000 you can get a complete data recording system (sans computer which you already have)and you can progress from wondering & parts replacing to knowing and making informed decisions. I recently bought a Dataq instruments model 730 for work, (I'm sure there are others that are equivalent, I have no tie to the vendor, just wanted to give an example). Three grand is a big chunck of change, but for folks who are heavy into the hobby I think it can save a whole lot of money and frustration in the long run and allow a better final end result. Data is good!