Once you have a good sounding and complimentary set of components and speakers one can very significantly improve their performance by methodically evaluating and adding carefully chosen improvements. Typically these are: speaker cables, interconnects, power cords, direct lines, power conditioning. Each is incremental… together several can add up to the level of a component level upgrade.
Typically one would not add a $5K power cord to a $5K amp. But that being a cost effective move is not unheard of. I recently added a $2K power cord to my $22K amp. The improvement in sound was very important and obvious. I would say, I got a sound quality improvement worth at least $5K. The boost I got from my direct lines was similar… so to my power conditioner. All this stuff adds up to a much… much better system. This is how you go from a good to a great system for the least amount of money.
While not often I have heard cables or interconnects that produced improvements worth nearly the total cost of the component… instead of upgrading the component.

