Eichman RCA's - what makes them so good?

I've just installed a set of these on a silver interconnect I have and the difference in details was very noticeable. The image has become very focussed with more depth and the micro details have also improved consideraby.

I realize the silver is probably responsible for the improved resolution, so is the design responsible for the improved imaging? Will the copper give me the same image improvements?

Has anyone out there tried both the silver and the copper (or gold plated copper)
- if so what difference did you notice?

Alternately - if you have only used copper
- what were you using previously?
- what differences did you notice?

I am using these on my analogue stage, which I thought was pretty good - until yesterday.

I'm thinking of trying the gold plated copper on the digital side - or should I just opt for the silver - the curious side of me wants the copper, just to see what the differences are, but the pragmatic side is saying that if I'm not happy - I'll need to replace them with the silver :-)

If it's the design of the rca that's more responsible for the improvements' then going for the copper would be more cost effective

Any feedback appreciated - thanks