Rank the tweaks, geeks!

Zero Gravity chair and weed

Ive tried a bunch and you truly want to hear a differance and possibly its a placebo effect but the two tweeks I done and without a doubt knew it was better was changing out the patch cable 5e from my Router/gateway to my streamer Node2I to a Linkup Cat8 22guage for $34. then I would say I did notice an improvment when I made a DIY Mogami speaker cable it definitely had a more refined sound and I want to say the IFI acPurifier does help outside of that I had high hopes for others like iso acoustics solation pads , interconnects and a few others and it didn't really blow my skirt up. Im a huge believer in putting some money in the source streamer- upstream , Garbage in Garbage out . Im thinking about getting liner power supplies for my router and my streamer now and possibly a galvanic isolator for the ethernet  , maybe something was wrong with my old 5e patch all along who knows , Im moving on. 1 absolute must is acoustics , I wrapped my entire room with a track curtain that has sound deadening material and that without a doubt is the best thing you can do to remove echos and get more detail from your current setup. 

raulwebster Piped in at 3.45 am Zero Gravity chair and cannabis. I’ll assume both were in use. Late night dude!

Raulwebster’s comment hit me like the proverbial ton of bricks. I’m taking about the chair. Spot on. My chair is so-so. 

Also would like a class trip to the Millercarbon joint. Like wow. 

While upgrading componets ( external and internal ) generally give you better or more pleasing sound . Two tweeks that suprised me were replacing the weight on my Rega RB300 tonearm to an Expressimo that lowered the center of weight and replacing a PS Audio power outlet to
an AudioQuest NRG edison ( does this count as " electrical " ? ) .
One I tried didn't like were tube dampers .

My list doesn't exactly follow the Op's list (my apologies, but then, I never have followed the rules) but the improvement I experienced when each was implemented was significant enough to warrant a mention.

Most important tweak in my opinion, though probably not an actual tweak is dealing with room acoustics. I dealt with mine electronically instead of acoustically because of cost, floor space and WAF. I do plan to explore acoustic options in the future.

The next biggest improvement was when I switched to fully balanced operation. The improvement in tone, dynamics and system noise was completely unexpected.

This doesn't fall into the tweak category either but the improvement was significant enough that I feel it needs to be mentioned, adding an active crossover between subs and mains. The difference in clarity and tightness in the low end was rather eye opening

Time aligning the subs and mains added even more clarity, space between instruments and improved imaging.

My last tweak is actually on the Op's list, component isolation. I haven't done extensive isolation and because of my penchant for loud, bass driven music the isolation platform under my TT is more of a necessity than a tweak. Other components I have used minimal isolation on so far are my subs and amps. I also have plans to explore isolation under my other components and improve the isolation under the subs and amps.