This makes no sense, but yet....

I had the sprung cables between my CDP and amp and they were unbearibly bright -

Try flipping them end for end and listen to them again.

how old is each pair ...meaning was one bought used and one pair bought brand new ?

They're all used. I believe I had the other pair in with the arrows pointing the right way, but I didn't look. This pair sounds a world better though. I can swap them in and out to see if I can duplicate the tizz. Good simple fix though if thats the case.

All things occurring with the performance of audio systems are not guaranteed to make sense. If everything made sense, man would this be simpler.

That is silly. Directionality of a cable is determined from a few purposely defined characteristics. I hate to say this and sound rude...but the quality control must be lacking if you experience an obvious difference. There is absolutely NO reason why a well designed cable would do this. Now if the plugs are the only difference as you state, then possibly this would be more of a hint as to what may be causing the difference. Still, they would have to be composed of different materials in order to be that obvious. If you use a cable that has no indication of directionality, except for drain wire purposes, it should NOT sound different plugged in either way. I only know of two designers who know how to manipulate this phenomenon. One can be found in a 6moons review (just look for the only award in the cable category), and the other is who specifically designed the cables for my systems.