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

For me it was an inexpensive power cord that was laying around for years, a Pangea AC9.  I have it connected to my Yamaha A S2000.  I've tried the stock cord on the Yamaha and then some of my other cords, (Wireworld, VH Flavor 4, Acronlink/Oyaide custom cord and a MAC). I've had lots of amps and integrated amps over the years, and this is the first time the Pangea contributed to making better sound. It surprised me because I had tossed it aside and forgot about it.  Power cord performance is such a crap-shoot and dependent on so many other variables in the audio chain.  Any inexpensive item you've come across that enhanced your system's sound? 
Added weight on top of cd player etc.Works great in conjuntion with my audio points underneath.  Try making your own ground loop to hang from youre neg amp or speaker post.I used a heavy inductor wire which made a huge improvement.Use terminal of choice.
chlv0ter, by any chance, did you compare the ASC tube traps to Owens Corning 703 fiberglass? I made my own OC 703 bass traps for the corners and wonder now if it's worth upgrading. Thanx.  
chrshanl37 and zavato, Nice suggestion and probably the best one here.  A $50 bottle of this stuff will do more than any $50 power cable I've ever heard.  Might I suggest Russell's Reserve Single Barrel as well.  
Why pay megabucks for a bottle? You can have the same effect for $15 with Ellington (Canadian). It makes the highs really sweet.
Mu metal foil shielding around phono step up ferment about 35 bucks.  

Auralex subdude isolation platforms under Ohm Walsh speakers about $100. 

Isoacoustics stands under various small monitors also about $100.  

The simple Monster power strip my preamp and source devices are plugged into cleaned up the sound for about $70.  

Auralex 24x24 inch acoustic panels at prime side wall reflection points about $35 each.  

I've bought gear on audiogon but not tweaks in that the cost for basic things that work like these are extortionist mostly here.