what are your top "audio bargins" in your system history?

Jolida 301 amp, older definitive technology BP series bipolar speakers almost 30 years ago, ESS speakers from the 70’s with the amt tweeter/midrange, rogue Cronus magnum 2 amp, ps audio ds jr (wish I still had for second system), and now the ps audio sprout 100 for a second system. 

I would have to say a Marantz 2265B reciever that someone gave me back in the early 80's  That was the beginning of my audiophile journey 

Recently l bought a used Spectron musical MK lll class D amp designed by John Ulrich and the old beast almost weighs 60lbs 

Years ago I purchased a VAC CLA1 MKII Pre, Counterpoint NPS-400, Clearfield Continental speakers with Synergistic Research cables for $300 and then spent $300 on tubes and a repair. I still have and use the VAC in my second system.

Bought a set of B&K Sonata monoblocks along with matching B&K Pro 10MC preamp for $450 about 10 years ago. Best bank for the buck I have ever come across. 

Wish I still had them.

New Large Advents $150

Klipsch Heresy "Decorators" $300

Infinity RS-II towers $400

ATI 1502 $150

I still have the Advents and the ATI amp.