One at a time. takes time and patience. When an IC is removed it will not sound as before until it settles again. My advice as a cable tester would be leave in for three days each IC and just listen. Trust your ears. You will know which you prefer aftr listening to familiar music.
In and out is only good for sex not comparisons. Stay away from special connectors as they will alter EACH cables performance DIFFERENTLY.
Takes time Emil and it is fun nd very educational. I have several for you to try if you like. JPS, TWL, Mad Scientist, Kronenberg, Audio research,Lenihan, etc.
charles