Biggest "bang for the buck" audio gear you have owned(in your history)?

This is very subjective, and your opinion on your own systems/items is all that really counts.

From the beginning to now, these would fit that category for me: (in no order)

Original Large Advents
Dahlquist DQ-10
Conrad Johnson ART pre.
Original Monster interconnects and speaker wires.
Nakamichi SR-3a
AR Turntable
Audio Research LS-12
Magnepan 1.6
Magnepan 20
Wireworld Gold Eclipse III
Audio Technica Electret Condenser headphones 
Magnum Dynalab Etude and 108 tuners
Magnum Dynalab Receiver (original)
And in those "early days" special pressings and imported Jazz albums. 

There may be others I am forgetting, but these were very good items along my journey. 

Well it's not my favorite piece of gear, not by a long shot - but purely based on "bang for the buck" I am hard-pressed to name anything that has squeezed out $400 of value as much as my old Bluesound Node2 that I picked up 5+ years or so ago.
Constellation Inspiration Preamp 1.0 and Stereo 1.0 - TAS 50 Greatest Bargains in High-End Audio

New Lyra Etna cartridge at half price.

Used Van Den Hul Grail SB - plays with the big boys
Parasound Halo stuff


Pass Labs for sure
Some ARC
I built a pair of Bottlehead Paramour 2A3 set mono-blocks about 15 years ago. They were a fantastic bargain at the time. They sounded great with efficient speakers and they were fun to build. Mine turned out beautifully. I sold them years later here on A-goN.
Just picked up a new 3B+ for $35. Sounds better than my BluSound that got banished to the back shed. 
Rectilinear 3A speakers
Rectilinear 7 speakers
GAS Son Of Ampzilla (original) Power Amp
Large Advent speakers
Nakamichi Dragon Cassette
Teac A3400 Reel To Reel
Accuphase T100 Tuner
Thorens TD125AB MK II turntable and arm
Shure V15 Type 5
Ambient 66 Speakers
Audioquest Indigo Blue speaker cables
Odyssey Stratos Extreme Power Amp
Golden Ear Triton One speakers

Audio Research SP10II. Bought in '85. Used thru 2010. My current Silverline Boleros. Quad 63s USA Monitors and an Threshold SA 3. All great stuff, then and still.
Placette passive Remote Volume Control--replaced a $15k Mark Levinson preamp back in 2001 and sounded better. $1295.

used it for 3 years and loved it in the context of a $250k system.
Dynaco Stereo 70.  Bought it used for $50.  Used it for nearly 30 years mostly stock, then added a VTA PCB, and new caps and tubes for another hundred bucks or so, and still use it in my main system today as half of a bi-amp situation.
@mikelavigne  - Agreed on the Placette. I had their 4 input passive "pre-amp" in my system for about 3 years. Great sound, very transparent. My buddy still uses one in his system and is very happy with it.
B&K ST140 power amps, Audible Illusions Modulas 3A and B, Shelter 901 series1, Large Advents, Theta DS Pro Prime dac and the Arci Lead Balloon turntable stand, to name a few. Enjoy the music
Transcendent Sound Grounded Grid kit built preamp.
Dynaco ST70 with original Mullard EL34's
Home built Crites "Cornscala's"
Carver C9 Sonic Hologram Generator $299 in 1982...still using this device now with Magnepans. 
Absolutely turns 2 channel stereo image to a 3 dimensional Soundstage when speakers are placed as the manufacturer recommends. In all the years I have been into audio this was and still is to me a giant killer! Push a button to completely remove it from the circuit and that huge image disappears back to flat 2 channel music, press the button back to holography...its a huge instant sonic upgrade. 
Space tech labs QA112 preamp, made my krell amp sound so much better paired with my apogee duetta 2 speakers.
@invalid  -  Space tech labs QA112 preamp

Noe there's a brand you don't see very often. How did you end up with it? Are you near their shop? I check out their website every once in a while. Their range of product is impressive.
Noe there's a brand you don't see very often. How did you end up with it? Are you near their shop? I check out their website every once in a while. Their range of product is impressive

I was looking for a new tube preamp and didn't want to spend a fortune, they had a lot of positive feedback and a used qa112 for $750 so I bought it. I also found a used separate power supply for it at the music room for $450, it's called a super rectifier and uses large 4 pin half wave rectifier tubes. 
Parasound Halo Integrated Amp
Actually anything in the Parasound Halo family.
Outstanding gear-Incredible support.
I was pleased to see the Large Advents mentioned.

 Large Advents
LBL L-100
Dahlquist dq-20s
Hafler Amp and pre-amp I built 
Roger Modjeski pre-amp

They all brought good music at great value but the only one I widh I had not sold was the Roger Modjeski pre-amp.


First “real” high-end system: Bose 901 series 3; Kenwood integrated amp, Revox reel to reel deck, Nakamichi cassette deck, Empire LP Turntable and cartridge; DBX-3BX compressor / expander; kit-built Dynaco FM-3 tuner. 
Bought new in 1988 Cerwin Vega D3.  They lasted forever and sounded good from day 1.  Not the best speakers in the world but a huge value for the money.
Also, Foobar2000 audio player.  Free.  Hugely customizable.  And when coupled with the $3 Foobar2000 Controller Pro app, super convenient.
3 pairs of Magnepans - 1 pair in each of the last three decades
Technics SL1200 turntable
Conrad Johnson amp
Apt Holman pre-amp 
...the multiple pairs of Walsh speaker I've diy'd.....
More time than $, but it's just another example of 'what we do for *G*'s, right? ;)
Bought a Parasound JC5 at release, owned for 2 1/2 year, sold it for nearly same price as I gave due to increase in prices. JC5 is such a remarkable amp for the money that I today own 2 x JC1+!! These cost me an arm and a leg, even tho they outperform in every way the JC5 will have a special place in my heart. It's just the best companionship I ever owned "bang for the buck" and it only cost med around $120 all inn all.

Can also mention a used JC2 I got cheap. I now run a ARC pre (the other leg and arm) with the JC+, but JC2 is actually thar good so its tucked away in 2 brand new Gant towels and stuffed under the bed as addict is to variable to temperature summer to winter. I just know to the bone that it will come handy some day..... I'm 38 years old so who knows what future brings.

Linn AV5140 loudspeakers, originally passive, now activ via Exactbox-i / Charkra / Katalyst with a conservative 100W available for each of 6 drivers.  Purchased in early 2000's.  More lovely today than ever.
The foobar2000 controller PRO app is now free (it might supported haven’t installed it yet)

That’s bang-in

Thanks for tip
Magneplaners, of course.

Love to see the large Advent's mentioned.  Mr. Kloss was a pretty smart guy--I mean, he invented the acoustic suspension speaker...where would be be today without that?  

Unfortunately, those speakers have been passed by in today's world, but KLH and Advent and the Videobeam are clearly major milestones in the industry and Mr. Kloss will always be remembered as the amazing pioneer he was.

Now, as for Jim Winey, well, he simply moved the bar so high that, thus far, no one has figured out how to move it higher.

Bloody hell man, It has all been best bang for the buck since day 1. 
  1. Began with JBL 4311's for 1/2 price in 1979, paired with an Onkyo TX 6500 and HK turntable with ortofon cart.  I conned a friend into transporting for me from Crazy Eddie's in NYC so I didn't have to pay for shipping. Crazy insane deal. But anyone who knows Eddie knows this prices are, well insane. That system progressed with the 4311's at the heart throughout and until till mid nighties' with the help of recycled audio in Boulder CO. Hands down the coolest place on earth for the budget college kid audio enthusiast. I remember getting my first credit card on Norlin Quad and heading there directly. Carver M500 and Apt Holman preamp for under $500. That was the limit on the card. Progress to 1997. Bought a highly modified set consisting of a pair of Infinity RF 1.5's a ridiculously modified Hafner DH-220 with 2 levels . Lower had over 80k uf Cap and a huge toroidal transformer and an early ps audio preamp with external power supply. $300.00. That system was built by a sound lab engineer from NL CT. Man if you are out there somewhere, I will forever be in your debt. I could go on and on. My current favorite system is dell windows app tidal precision laptop on battery> Peachtree nova pre> Adcom 555 (crown jewel of the system) DIY based on Blue Sky audio mods so graciously posted and some poaching from hoppe's brain parts list and all silver and copper inside > Dunlavy SM-1 and a modified Adcom GFA 5500 mono channel feeding a Dunlavy SC-S2 via active crossover - sorted. All for under $5k .  I have to say, I could be the master of audio nirvana on a budget. Anybody ? Cool mentions above, but come on guys - systems?
About 14 years ago +/- I bought a pair of McIntosh Mc501 mono block amps to drive my 3.6 Maggie’s.  The make the Maggie’s sing as they have the power and current to feed them what they need.  I bought them used, they are still in terrific condition and if I were to sell them (Not!), I could get what I paid all those years ago!

That IS getting your money’s worth out of a product!!
Pair of mint Onix Rocket stand-mount speakers mounted on Pangea stands I picked up for $20. 
Over time I'd say an SME 3009 III on a Micro Seki DX1000 ('78) and my current LS50's. Still can't beat the KEF.
DB Systems db-1A preamp, tone controls and power supply, bought used then upgraded.  
Jeff from Silversmith recommended this with an explanation that the common ground added extra length to the signal path and degraded the sound so a  $2.99 3 to 2 prong ungrounded adapter would provide similar benefits as a high end power cord and that many cords actually  just remove the ground.

I finally dug up an adapter and inserted it between the poser conditioner and the wall.

Worked for me.  It's bigger with a quieter background similar the the change his $1200 speaker cables made on a demo I listened to.  I don't own his speaker cables but will buy him a beer if we meet up again.