Right. There are only two places where matching is important, cartridge to tonearm and amp to speakers. Cables, depending on their purpose, are either good (sound like nothing) or bad (sound like something). There is nothing in between.
If you have a bad room you have a bad system and the solutions are to use headphones or find another room.
A dealer's job is to make money. Survival is always #1 with humans. I know only one dealer who could care less. His shop is a retirement gig and he is all set in terms of finances. Not that other dealers are not OK to deal with but I have never experienced a dealer telling anyone to go to another dealer to buy the competition because it is better. I worked in that system for 5 years from a big box store to the highest end store in the neighborhood. The only difference was the degree of sophistication.