The dealer is obviously blowing smoke and trying to influence you to buy the expensive cables. It was an excellent test to indicate that the dealer could care less what it sounds like, as long as you buy the $$$ product from him! lol.
As far as your audiophile friends, this is a prime example of "pre-conceived notions" getting in the way of true objective listening. An audiophile can easily enter into a listening session with the idea that Cable X will sound better than Cable Y, so the mind plays tricks on you and influences you to actually think that way. It is very difficult to "leave all pre-conceived notions" at the door and truly listen objectively. It is a learned skill and takes time to figure out how to truly "listen" instead of "seeing" a particular product name. I have determined myself that $$$ cable does not necessarily mean it will sound better. We actually determined that plain old 12awg stranded OFC copper speaker cable sounded better then a several hundred dollar Nordost Blue Heavan. The 12awg is actually a pretty excellent speaker cable. In other extensive power cord and interconnect testing, I do believe that cables make a difference, but I have not yet gotten into R&D on speaker cable. I still actually using a double-run of 12awg OFC stranded ($15 for 50 feet from monoprice!). Eventualy, I will get into this. Based on other cable R&D, I think that the Neotech NES-3002 from VHAudio would be a excellent step up (being that individually insulated 21awg solid-core OCC copper conductors). Based on interconnect R&D, I believe that the braided Kimber 8TC/12TC would be good alternatives for testing as well. Even though Kimber conductors are still stranded, there are only about 7 variable gauge strands in a single insulated conductor. This is close to solid core and much better than normal stranded cable. Ahh, future testing.