Best "Bang for the Buck" you have owned?

B&W DM-12 for $99.00 on eBay.

It really is amazing what a great system you can put together buying older stuff on eBay.

A Belles Research II preamp for $195 in the early 80's. Could not believe how much better it sounded than the NAD one I had. Couldn't bear to part with it after it had been in a closet for 15 years hoping my son would catch the audio bug. When I finally realized it wasn't going to happen, I traded it with my B&K 202 amp which is my second best bargain. That was from the mid 90's for $400 was going to keep it and replace the Belles for a preamp with a remote, but was able to get an incredible (3rd best) deal on a Plinius integrated 8200MKII ($1600 with a volume/mute only remote) that is now 15 years old. Can't see ever getting rid of it. 

4th is a Music Hall MMF 5 in early 2000's that introduced me to the belt drive world which sounded so much cleaner and alive than a Phase Linear 8000 that cost way more than that 15 years earlier. Thankfully, that broke or else I might still have that and not know what I am missing. My Rega's since then have been unfortunately at list or within 10% of it, but I still consider them killer values.

Ohm c2 speakers ($600 new in 1968) when I was 16 and advised to put the most $ into the sound-producing component and used (now refurbished) Ohm Walsh 4’s ($400 used) bought last year.   
Oh, I also had a rather wonderful Pamela in my youth ... thanks for stirring those memories!

Naim Nait 2 and MD Étude tuner. Bought new in 86 and still using them

Auralic Aries Mini open box for $499 from Audio Advisor. They included a whole year of Tidal free! It probably got discontinued as its margin was not as high as the higher end Auralic options.