For me replacing my Node 2i streamer with Sonore Optical Rendu in my main system was an eye opener. I was skeptical about the impact on sound quality (0's are 0's and 1's are 1's, right?), but I was really surprised at how much it lowered the noise floor. Also made me a believer in equipment that generally reduces noise floor.
Disappointment: Upgrading from Parasound A23 to A21 (both were sold many years ago). The difference, in my system at least, was marginal.
Disappointment: Upgrading from Parasound A23 to A21 (both were sold many years ago). The difference, in my system at least, was marginal.