Upgrade with best price/performance ratio

Just wondering what was your upgrade with the best price/performance ration in your audio journey ... like upgrading an IC, preamp etc ...

Let me start:

-Corian pieces leftover from kitchen upgrade project

out of boredom I used the Corian chopping boards and put them in between the shelf's MDF board and BDR cones. The effect was a big surprise ...

- much quieter background, solid bass and cleaned up mid and treble.
Similar story, best price/performance ratio: Blutack on shelf supports to isolate wooden shelves. Second best, powercord for my amp made with parts from Home Depot ($17). Third best, Fusion/Auvio interconnects from Radio Shack ($15-20). Honorable mention, ash chopping block placed under my CDP ($18 on clearance from Home Depot). Not sure this counts, my brothers old Thorens TD150 MkII (free).
I didn’t think so at the time, but constant urging from some friends of mine here said “just try ‘em… and see for yourself”.

Some of these I was talked into, other’s came to me naturally.

So here goes…. From low to high:

Fubar 2000…. Free
Speaker positioning … free but tedious
Dedicated 20A ckts …. $25 ea when ordered with the new house
Plywood platforms for rack bases and speaker stand bases and sub woofer. $20
Herbie’s Peak tube rings….$ 20ea
Herbie’s Iso cups w/Ebony balls …. $20 ea. new
Bright Star Iso nodes under shelves on racks…$ 25 new
J River Media Center…. $40
1 Click DVD Copy Pro …$50
Stereovox XV2 digital cable. …. $ 110 preowned
VD Power III pc….. $100 new
M2Tech Hiface 24/192 BNC… $187 new
Oyaide T510 BNC digi cable….. $220 new
Phase Tech PC 6.5…. $30 used/ $250 to rebuild
VooDoo power cords… assort’d prices
Phase Tech PC 10.5 speakers…. $600 used
Odyssey Stratos plus, SS amp…. $1250 new
Bel Canto DAC III… $1700 preowned
Butler TDB 5150 5ch amp…. $17500 preowned
Dodd 120w MK II mono blocks …$2500 preowned
Thor preamp TA 1000 MK II…. $3400 preowned
Silverline Sonata IIis…. > $4,300 … new.
Dedicating & optimizing the listening room… $6K so far

Most of all though...
Being an American sitizen, Honorably discharged Veteran, single again & now retired…. Priceless
Yes, speaker positioning and appropriate connection to floor - very high on the price/performance list (very low p:p ratio). I also felt replacing all fuses in my amp with HiFi Tuning silver fuses and adding aftermarket PC to my CDP provided big performance boosts for not tremendous amount of money, but both were well over $100 so a higher price/performance ratio compared to those I listed above.
Furutech fuses make a surprising difference for the small investment whcih they require.
(disclaimer: I am a dealer)

Jim Smith's book Get Better Sound for $25 or $30 is great also. i do not sell that though :-)
Room treatments. Nothing can sound right in a bad room.

Ferrite snap-on core noise filter. About $2 each. Put one on each end of all
digital cables and power cables saved me from buying audiophile brand cables.

Replace batteries in my Vandy 5 crossovers. It is not really an upgrade, more like
a maintenance but the effect is really day and night.
My Machina Dynamica (Modified) Clever Little Clocks with two P.W.B. Electronics Memory Foils on each battery!.. foil@belt.demon.co.uk
Hello Buff : I read your post on Audiogon re the Furutech fuses. What were the differences you heard and in what kind of equipment ? Have you compared Furutech to other high end fuses? If so, what are your impressions ? Thanks tubey / Vasil
Maestro ac outlets...$79 Made my cheap entry level system sound like a much higher priced system !.. far less HIFI sounding to more believable.. more REAL sounding !.. for ONLY $79 !..
by far the best price to performance ratio, cleaning all your contacts with pro gold, jewelers polishing cloth and pipe cleaners is all you need, it makes a huge difference, funny how I know so many audiophiles that will spend thousands to get maybe a different sound, but wont spent less than twenty, for BETTER sound.
Mint LP protractor
Scotch Foam Tape between cone footers and tile floor
Two granite slabs on tops of sub woofers
Furutech receptacles
Thats easy , dressing cables , costs pennies , cleans up the sound . Down fall is that in an elaborate system it can take days .
The new and improved BOSE 901 series 6 MK2's have the best price/performance ratio that I have ever seen in all the years I have been in this hobby!..
I gotta second Unsound here...I discovered ear cleaning when as a pro guitar player for WAY too long my abused ears used to get clogged with wax. Ear cleaning with the bulb thing is really pretty great, and you can use the expelled wax to make a really creepy candle! I recently found an interesting phenomena while listening to a test CD...during a frequency sweep while sitting in the "sweet spot" I found an AMAZING change in sound when turning my head a little...so my cheap tip is this: Don't turn your head.