Know of a "Dirt Cheap" tweak?


I am looking for tweaks to improve the overall sound quality of my audio system. I recently purchased some TPC contact cleaner and it made a believer out of me. I noticed a signicant improvement, as if a veil was lifted my system sounded more clear and transparent. Bass got tighter too. Do you know of any cheap tweaks that have made a SIGNIFICANT improvement to the sound quality of your Hifi system...let us know... :-) Comments welcomed!
kasboot
Completely agree with Kavakat1. Reinforcing my subfloor from beneath the crawlspace has been on my to-do list for some time now. Finally got around to it a few weeks back. I'm very pleased with the results. I cemmented 3 pillar blocks with 4X4 attached to the joists. Additionally I reinforced the joists by screwing 2X4 on each side butted up to the subfloor. Maybe overkill, but now my system sits on a much more solid foundation, close to a solid slab of concrete. Total cost was approx $200 in materials and 8 hrs. of labor.
Plus you get to spend time in the narrow confines under the house, where, I assure you, no one is going to come and bug you. 

Last week was lube time for my TTs.  This time used 5w30 Mobil One Synthetic.  It might be expectation bias but I like what I hear.  
The cheapest one I know of was mentioned (I think) by Stereophile: take your glasses off. Works only for the eyeglass wearers of course, but for the "lucky ones" it provides an extra benefit of Total Immersion into music. You wont be able to read/text/surf, only music! Goes well with "Immersion Box" sets by Pink Floyd ;-)
KAVAKAT1  be a man and fight for the dedicated listening room: its your house!! When I was younger I could do it, not any more :-(    Thats why you see headphones and portable CD player next to my "sweet spot" Big'n'Loving family successfully neutralizes all the benefits of my hi-end rig...