Cost Effective System Improvement?


My hobby is to get the best possible sound IMO at the lowest possible cost. My system:

Tekton Electron Speakers - Upgraded
Doge 10 Tube Amplifier (generally 30WPC in Class A) with Psvane KT88-TII, GE 5751 3 mica black plate preamp tubes, and NOS Mullard CV4024 phase inverters.
Denafrips Pontus DAC
Canare 4S11 Speaker Cables

I listen only to TIDAL Premium through Bluesound Node 2i using the BluOS on an android tablet. I often listen to vocals and use the following as test tracks:

Vaya Con dios “Don’t Cry for Louie”
Dave’s True Story “Chasin’ The White Line Down”
Dead Can Dance “The Wind That Shakes the Barley”
Harry Nilsson “Without You”
Glen Campbell “By The Time I get To Phoenix”

I would like recommendations on what I might do for a cost effective improvement. I would consider spending $2-4K for different speakers or amplifier. The speakers and/or amplifier would have to weigh less than 80lbs. My back is 75 years old.

I appreciate your recommendations.
chinook9
The best, most effective and probably cheapest upgrade is to improve the acoustics of your room.  A dozen or so 5' to 6' artificial Ficus trees scattered around the room will improve the sound more than new equipment.  There are easy to find at discount home dec stores.
If you really are serious about squeezing out the absolute max per dollar, this will be a lot of work, but I highly recommend studying mahgister. Where most of the work comes in, a lot of what he does will look to be honest rather kooky. But this is where you have to really study and learn your stuff. For example, what looks like empty old gas cans with soda straws coming out are helmholtz resonators. A helmholtz resonator is really any container (volume) of air with a restrictive passage leading in and out. Air pressure in the room flows through the passage into the container and back out again, losing energy in the process. The volume inside, together with the diameter and length of the passage, determines the frequency of sound that is most efficiently absorbed.   

Most people just buy these things and so never do understand what is going on. The design can be worked out mathematically, but then you have to know what frequency you want to tune, and work through the math. Or you can do the whole thing by ear, or start with a ballpark math estimate and fine tune by ear. Or use existing product designs as a starting point and creatively build and tune your own.  

This is just one example. His room and posts are chock full of them. Like I said, a lot of work. But for someone with plenty of time and willing to do the work I think you will be surprised how far these kinds of things can take you.
Thanks millercarcon but most people dont own an audio dedicated room...And my system is impossible to live with it and a wife in a living room...

I created it to prove to myself i could reach near the highest Hi-Fi to my satisfaction with basic good choosen gear yes, but embeddings controls at NO COST or very low without buying nothing by recreating some basic ideas or some costly devices...

Most people are better to be inspired by what you have which is Hi-FI, more beautiful...And more costly... Though...

 Anyway the truth is simple:  WE embed everything before ANY upgrade....