Using 2 different brands of interconnects?

Some Good advice here. I was skeptical of the benefits of cables. I had purchased the entire gamut of BlueJeans Cable and thought I was done. But, I was testing out CD players and ended up bringing my entire system including speakers to compare and contrast players on My system. After trying 7 different CD players I chose a Cambridge.

But then, just for fun I tried 3 different Patch cords. I only changed one set, from the source, CD player into my Pre-amp. When I tried the AudioQuest Waters the change was HUGE. The sound opened up, I heard separation and clarity.  I couldn't believe my ears. I didn't want to spend $500 for two wires. But it had to be done. And it was well worth it. 

BUT! I should have stopped there? I went down the very expensive trail of wires. I have a Pre-Amp and two Amps. All of which take wires. The upgrade to all AQ' Waters made a difference. I then went to Earth's. Subtle, but a change. Speaker wires too. Oaks. Smoother. No one with ears could deny the changes. But... was it worth it on my system? Maybe. To do it again, I would definitely change the source wires to quality ( side by side test if you can ) Change the speaker wires and be done. 

BlueJeans were a good upgrade and they sounded equal to the AQ Gibralters. But for me the sweet spot was the Waters. Your ears may vary. But don't let anyone tell you wires don't make a difference. 

I would imagine if you did a blind test you would not be able to detect a difference.  Someone should do this with twenty people present,

Wrong Larry, I did a blind test. 4 different sets of wires. I sat in the chair, listened to one minute of the same music, while the salesperson changed the wires out. Did it many times. I could easily hear the difference and was able to actually identify the names of the different wires. 

I find that people that are nay-sayers usually have never ever tried anything. They just like to spout their opinions. 

I would imagine if you did a blind test you would not be able to detect a difference. Someone should do this with twenty people present,

It's been done countless times.

I ran a blind speaker cable test @ AES in the 80s. After a few days running the test, I wrote on my page "Too tired to tell." Up to that point, I had 84% correct. At the end of the test, barely better than 50% correct. Ditto others in other tests [Tube v SS and Absolute Polarity]. Those that did well in one test usually did well in the others.

Note the tests were just rooms in [convention center? / hotel?] with poor sonics, moderate ambient noise and random interruptions.

An interesting side note is that towards the end of the test several listeners wrote C or N or ? for their choice in some tests. When we examined the tests, the non A/B choices correlated fairly well. We later determined the DAT error correction was messing up on the tape which had been played 100's of times. Sometimes the test is faulty. Any showroom comparison is certainly invariably so to determine suitability for your system unless it has the same equipment and room as yourself.

Some people can tell almost all the time, some about half and some never. That so many got it right in such abysmal conditions strongly endorses for audibility.

The AES committee running the tests concluded there was no difference.

When I ran an analog design team, we had some brilliant engineers. Some had great hearing and others not so much. We did completely blind testing in our sound lab. The candidate sat in the listening position and had to identify changes. The candidate had no communication with the test personnel as one could not see nor hear the other. They got to hear A and B as often as required. Then they had to choose A or B from 20 random playings. Guessing was not permitted. Acceptable choices were A B or ? for can't tell. Some did consistently well and some not.

Note that in some systems, a part / cable / component will be identifiable by some ALL of the time and in another system NONE.

I once participated in an evaluation of a new digital console for one of the major Japanese manufacturers against the competition. After the first play of each, I got up and left the room. The manufacturer's representative came out and asked me why I left after only 1 play. I told him that was all that was necessary. I re-entered the room when the blind testing started and got it correct 100% of the time as did a few others. Like any such test with a random selection of participants, there were some who could detect no difference.

Some will say but "There's a big difference between an amp / DAC / digital console and a mere wire." All are moving energy from one place to another, so if one device can impart a flavor why then can't all.

Those who can tell freely admit there are those that can't. If only the reverse were true.

Amen