I just wanted to write a post about my cable experiences, and now I see, you are talking about cables... :)
So, after buying my IE80, in the first month I had bought a 6N OFHC silver plated upgrade cable, on eBay, from Hong-Kong. It was around 40 pounds.
I noticed, the sound is brighter, more balanced, richer, especially the highs are more opened, more sparkling.
After 18 months this cable broke. The welding between the cable and the connector to the earphones broke... (Normal use.)
Guarantee was 1 year, so I had to find out sg, as I do not have fine welding equipments... :)
Now I had to return to stock cables for 2 weeks, and man, I can tell, I do not like it. The debate, if upgrade cables are worth the price or not, is clear for me now. Stock cable is much less balanced, less rich, less enjoyable... Sounds poor compared to my upgrade cable, which I used for 1,5 years...
I was thinking about buying a pure silver cable for 160 pounds... Almost the price of the IEMs...
But finally I decided to buy MKIII upgrade cable for 84 pounds, eBay, Hong-Kong...
They promise a richer sound, and I think, pure silver cannot make such a difference, that worth the double price of my MKIII... (Just like some review sites stated as well...)
Not to mention the 2 years warranty...
So, my personal conclusion is:
It is definitely worth to buy an upgrade cable. But not necesserily the 160 pound silver one... (However, I havent tried that one yet...)
If I was happy with the 40 pounds silver plated one, I think, I will be happy with the 84 pounds MKIII.
Update in 2-3 weeks. :)