The first was my first stereo in (dare I say it) the mid to late 60's. AR4X speakers, a Fisher Rec, and a Dual TT.
Second years later, after dozens of changes, was an AES AE3 tubed pre. Wow, I could now really hear the wood in the guitars.
Third was Analysis Plus Silver Oval IC's.
Forth and most recent, a year or so ago I replaced my Cardas Cross Speaker cables with Paul Speltz's Anti Cables. Wow and considerably cheaper too.