Value of upgrading only 1 set of interconnects?

In my experience there is a definite value to upgrading one component at the time; be it an interconnect or anything else in the system. Of course different connections may have different effects on the overall sound of the system. In your case where you are only looking at 2 sets of interconnects you could start by upgrading one set, listen for improvements (or otherwise!) then change it with the other set and listen again to the effects of change. Then you can decide if it's worth upgrading the second set as well (or indeed was it even worth changing the first set).
For what its worth; I have Synergistic Research interconnects throughout my system between all components and they sound superb but I did not upgrade all of them at the same time. Once I bought 2 pairs I was enabled to replace  each component at a time and evaluate the change for myself.
I also agree with the other comments here that you need to hear significant improvemnt in the sound quality to your ears before upgrading interconnects. What I am suggesting is not about the cost of the cable. What may be an open and liquid sound to me you may hear as sterile sound.
One thing is for sure and that is the right interconnect makes a huge difference to the sound of your system. It's a lot of fun trying to find the right one for you and your system.

Mort  

@cleeds 

"Don't be silly. If that were true, the Internet wouldn't work."

Could you elaborate, please?

I'm going to go against what most people have stated here on the thread but. In my years of listening to systems and changing cables I have found the preamp to amp interconnect is the most important and most apt to changing the sound of a system when upgrading. Simple reason being that you're volume (or in this case the electrical power) is lower than the one the source components use normally. Usually about by half. Because we never listen to our systems at full volume. The source components almost always see full power during a song.

So to make a long story short reserve your best interconnect for the preamp to amp connection which usually needs a much lower noise floor and better resolution for those lower volume levels. 

OP: you didn't say WHY you feel the need to change cables. Please enlighten us.

@pellethead,

Thanks for the perk.  Love the name btw.

Bob