When I worked at Quatre, we would often receive the better gear of the day for comparison.
I remember the Rappaport preamp was the best thing out there. (I strongly disagree with an early post). The Rappaport wasn't built that well, but if it didn't shock you, it worked and worked great. I remember someone brough in a gorgeous, state of the FET preamp from Infinity. It sounded so bad we wondered if it there was something wrong with it. We also tried the Apt Holman, which I don't remember being terribly impressed with. People would rave about the (Holman designed) preamp section of the Advent 300 receiver (I loved the look - very military), but didn't think the preamp was at all impressive.
The Denons were good MC cartridges, but I remember the hot setup was the Supex. But they kinda varied from unit to unit. When you got a good one - wow - was it ever good. The "bad" ones were not bad, but a good one was simply awesome.
I remember someone bringing in a pair (this was mid-to late 70's) of speakers from a very new company called Vandersteen. They were the 2s - which sounded very good indeed. One of our dealers brought in another new-ish speaker at the time - the Rogers BBC LS35a's. Very impressive little speaker. They still sound pretty good.
And we were awed by an old pait of AR3a's with the DG250 - man did that amp have good bass - it just transformed the AR's bottom end which tended to be on the tubby side.