Digital Cable Choice; how critical is it?

My experiences have shown that there are dramatic sonic differences between digital cables. I cannot explain these differences in scientific terms but I am sure they exist, zeros and ones notwithstanding. One thing of which I'm sure, the differences are not "placebo" effect. Does everything that can't be explained by science fail to exist?

Nsgarch - Just work to date for a recording device. The one o these days plan is to get the meaningful measurables on my audio system recorded to hard disc for reference and troubleshooting, and then too start digging into things like does the dc buss on my pre amp wiggle when the fridge kicks on & does this create a measurable difference to a constant frequency wave output measured between amp & speakers.

VERY... I've owned the i2digital X-60 for the previous two years. (This cable is no slouch) http://www.i2digital.com/splash.html#

I just purchased a Harmonic Technology Cyberlight. Very obvious differences that even my girlfriend easily hears.

(1) Very faint sounds that were never heard before come thru easily.
(2) When the system volume is high, instead of the music sounding loud, it sounds like real instruments in your room, all very relaxed sounding.
(3) Lower noise floor
(4) Top to bottom improvement in reproduction.

I could go on and on, but will stop here.

Neil (Nsgarch): My remarks could have been more clear....Please let me clarify. My first ICs were Apogee Wyde-Eye and I used both 75 Ohm and 110 Ohm, with a CEC TL2 and an Audio Logic M34. Between the two Apogee ICs I really did not discern much difference, with only a very slight preference for the 110 Ohm. Both cables were 1 Meter in length. I then moved from the 110 Ohm Wyde-Eye to 110 Ohm Kimber Orchid, which was longer at 1.5 Meter. I would not choose to state that the length was a significant factor, but the improvement in clarity and detail in moving to the Orchid was very revealing and very suprising. Until that time I was in the camp of 'can it really make that much difference?'.

I have had only minor exposure to ST-Optical as my transport does not currently have a working ST-Optical output. My only experience with ST-Optical in my system was with another transport and that experience was that ST-Optical was suprisingly good.