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

I acquired an Audio Research VT130 as a "throw it in" (that would be for free) while acquiring an SP15.  Someone had "adjusted" the left channel tube bias and it was blowing screening resistors. Once that was rectified I was amazed by the depth of stage the old gal had. Free is a hard price to beat. 

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.