Value of upgrading only 1 set of interconnects?

Late answer and I agree with Lak.  One IC upgrade can make a big improvement.  Most of the time when I have added a second one very little if any difference was noticed.

As you get more experienced at this and in the sound you are hoping to achieve, you will generally get little to no satisfaction when you upgrade slightly or it was a sideways move.  I like what the reviewer for Dagogo, Doug Schroeder, said about upgrading cables or really anything in the system.  He says if you have to strain to even think you are hearing a difference for the better, then it wasn't worth the time and money to do it.  He won't upgrade to a better cable unless it is significantly better in sound--and, for the most part, it will also be a significant jump in price, too.  I putzed around for awhile with very slight upgrades or some changes that weren't even noticeable.  It was when I started doing what Doug suggested to me--upping the cost about 50%--that the changes made a significant difference.  I'll agree with those that said it depends on the sound of the system whether staying with one brand of cable is a good idea or maybe throwing a different brand in the mix that has strengths that go with the different strengths of the cable you already have and liked might be a better way to go.

Bob  

@dorkwad - Well said, Bob.

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?