Has there been any inexpensive item that enhanced your system's sound?

A lot of great feedback here. For me, the best "inexpensive" tweak that I made was buying Solid Tech Feet of Silence. They were recommended to me by a high end audio dealer who actually didn't carry them. He said they will have virtually the same performance characteristics no matter what surface I place them on. He was right- and the vibration reduction markedly improved the soundstage in my system. The better news was I was able to keep the rack I was using which I find aesthetically pleasing (high WAF) and fit my application well. So, I feel like I have the best of both worlds. 

Absolutely consider smartly placed room treatments. Even "free" ones can make a significant difference. Draping a thin tapestry over my flat screen behind my system cleaned up the musical presentation dramatically! $29! As someone wrote earlier, pay attention to first-reflection points. 

Power conditioner (the right power conditioner) and power cords also made a significant impact on my system. However, I would classify them as inexpensive tweaks. 

And don't forget why started down this path in the first place... for the love of music. Cheers!

Thanks Meerzistar.  I think replacing is the best thing as you are really suggesting I think.  I did use Deoxit on all my AC cable connectors and that was a big help.  But I have so far not tried to clean the wall socket receptacles.  And listening to what you say I won't now.  Trouble is I can't replace my receptacles in my rental apartment, so doing this may have to wait.

In the late 90’s I purchased a Naim Wiremold power strip for $60.00. 9 heavy duty outlets wired in series connected by a busbar. Solid aluminum case. No lights, no fuses, no off/on button. Basically all power, no filter and a heavy duty captive grounded power cord.

Approved by and endorsed by Naim Audio to be sold by Naim Audio distributors to be used with Naim gear. Non current limiting. Instructions were to plug the highest current draw closest to the power cord and work your way back through your system to the least. Amp, Preamp, CD, Dac....... best $60 bucks ever.

They went out of sight for a gew years but AV Options.com carries newer higher performance versions along with Cryogenic properties. Additional power Cords can be purchased as well.

If interested, Google Stereophile.com and search Naim Wiremold.

N

Ayre Irrational but Efficacious! CD. I just got it today and ran it through my system and though I don't know what the heck it does, it does it very, very well.

If you decide to get a copy, go with Elusive Disc as they have the best price and lowest shipping costs. 

All the best,
Nonoise

Having my vintage JMW tone arm and junction box rewired with Nordost Valhalla 2. The cost for labor, wire and return shipping from VPI? $150. The improvement over the original Discovery wire? Phenomenal. I laughed out loud.