I have had the most improvement from source to preamp. I just auditioned a pair of Audioquest Dragons vs. Thunderbirds. I was astounded that the Thunderbirds held their own from preamp to amp; however, the Dragons were substantially better from source to preamp.
Where to put best interconnects
Getting a new tube pre-amp into tube mono blocks with one CDP as front end. Will have one very good, new set of XLRs to use and one good but much older set, each at 1.5M. Where to place the better set?