Most useful tweaks that are sensible and really make a noticeable improvement

Dynaquest I completely agree with your assessment of geoffkait tweaks in the most part. It's difficult to tell when he's serious about a tweak or just throwing crap against the wall to see what sticks.
Kinda like his panties when they wad. Sure hope they don't fall on his sandwich. 
In any case Geoff is entertaining. 
Batmobile, I do wonder if he really believes all the wondrous fatasies (or are they) but like legends there is usually some fact behind the tale. I'll try the TC and it will be either an improvement or snakeoil. 

Thanks, Gill.  Geoff, I'm sure is an OK guy but perhaps a bit overly obsessed with tweaks and this forum.  Me?  I just love listening to music and changing my system now and then to keep things interesting.  I have no interest in wasting time and ridiculous amounts on money on esoteric accessories and science-defying tweaks. 

Recently, while temporarily cooped up in my mother-in-law's guest house while we looked for a new home in the DFW area, I was listening to some music blue-toothed from my phone to a cheap soundbar.  I found myself tapping my foot and singing along.  I caught myself....thinking goodness...it is just a soundbar.  But it sounded good and I was enjoying myself. Too often, I think, we forget it's really more about the music than the system and we should be listening to the music and not our latest tweak.

High fidelity MC O.5s easy to use- good bang for the buck

There's snake oil, and then there's the good stuff. TC is the good stuff.