I think it's a toss-up between the Thiel CS3.5 speakers, which were the first true high-end speakers I really listened to (couldn't afford them, wound up with Thiel CS 3s instead--this was in 1986, as I recall) and the Well-Tempered Turntable (got it in 1987), which made me realize that my vinyl collection was a lot better than the CDs I was listening to at the time.