Like your entire system, it's a chain. Changing any one thing will change the system. So you might hear the most difference with any one of these depending on your system.
While speakers (most people think) will change your sound the most, I have always felt that the preamp is the heart of the system. Everything goes through it and if it has faults, they will be passed on to the speakers no matter how good they are.
So, if everything in your system is equal (and this is seldom the case), power cords and power conditioners could make the biggest difference as long as they are of equal to or of higher performance as the rest of the system. Then I would upgrade the speaker cables, so that I know the best signal from my amp is getting to the speakers. And finally, I would upgrade the interconnects to make sure all my source components are sending the best they can through the system.
Some people have good luck with mix and match, but my best results have come from using all of one brand of cables in my system (YMMV).
While speakers (most people think) will change your sound the most, I have always felt that the preamp is the heart of the system. Everything goes through it and if it has faults, they will be passed on to the speakers no matter how good they are.
So, if everything in your system is equal (and this is seldom the case), power cords and power conditioners could make the biggest difference as long as they are of equal to or of higher performance as the rest of the system. Then I would upgrade the speaker cables, so that I know the best signal from my amp is getting to the speakers. And finally, I would upgrade the interconnects to make sure all my source components are sending the best they can through the system.
Some people have good luck with mix and match, but my best results have come from using all of one brand of cables in my system (YMMV).