I found this article:
http://www.audioholics.com/techtips/...erconnects.php
I think it sums up the this whole topic very well!
The point of diminishing returns is a hard one to equate - it depends what your starting point is.
For example, you could purchase a very cheap and nasty HI-FI system (say $100). If you replaced the speakers with a decent set, you would almost certainly hear a difference in quality.
If you replaced only the speaker cables, you would hear no difference.
I would only spend my money in this order:
1. Speakers - If the speaker isn't capable of accurately converting the electrical signal, then any money you have spent on the rest of your system is wasted.
2. Amp – of sufficient power and quality to drive the speakers to the desired level
3. Source (CD player etc) – as the saying goes “crap in crap out”, I don’t believe there is much to chose between the quality of any two CD players these days.
Speaker cables don’t even figure!
As for gold plated optical cables......don't get me started on that!