Best DIY tweak?

Oh yeah, another DIY tweak would be cleaning all the connections between cables with alcohol to remove any oxidation that might get in the way of the signal path. Worth doing at least once or twice a year. Try it, and you will be amazed.

Replace steel speaker driver screws with solid brass screws; dramatic results!

That's not a tweak, man.......that's a mod. Where's your entrepreneurial spirit?

Hey Darosenb: I do that all the time! It sounds like i just doubled the amount of drivers in my speakers!
Cheers!

I would change the question to:
The best free, or nearly free tweaks.
(nearly free is a few bucks... never more then a Ten$)
#1) Shining all silver spinning discs. (CD and DVD): I now use Meguiars "ScratchX" to clean, smooth and polish all my discs.(under $10 a tube, lasts nealy forever) (I use Viva paper towels, and they 'usually' work well, once in awhile the paper towel will scratch a bit, then I send that roll to the kitchen... and get another one...)
#2) computer chip antistatic foam (from like Radio Shack) around the IC's in a DAC. (this tweek was reported YEARS and YEARS ago in Stereophile from the ?Danish correspondent.. I like it.) again under $10.
#3) Rubber chemical bottle stoppers everywhere... $1 each.. I have dozens of size 10 around, on, and under...
#4)Caig Deoxit cleaning on all the connectors and A/C plugs
#5) Teakwood blocks from a Goodwill find Kitchen cutting board, or a cheese cutting board.. $2 or so, but you have to find a REAL teakwood board, many branded as such are not. has to be heavy 'greasy' feeling wood. (not that it has kitchen grease on it!) I have many 2" cubes..
#6) speaker cable risers, cardboard tubes cut into 2" tall, with a "V" to hold the cables. Free. If toilet paper tubes turn you off, use the paper towel tubes..

I gotta hand it to you, Liz..........