You ask good questions. Your system seems pretty well balanced.
Looking over your system. I think the biggest bang for your buck would be a good quality power conditioner... I recommend Shunyata or Isotec. It has the advantage of improving much of your system. If you plan on upgrading your system, then getting a good one will provide benefits far into the future. Since modest audio components basically scrimp on power conditioning in the component, external power conditioning can do a lot. Audiophile products like CDs, DAC, preamps tend to weight 30 + pounds... mostly from internal power conversion and conditioning... so that is one of the aspects not fully addressed in modest equipment.
Your integrated should be plugged directly into the wall. All power conditioners limit the amp. So, you are likely to get a notable improvement with a good quality power cord.
If long term you want a much better system, then the question of when to stop doing little tweaks and upgrade components. You don’t want to put too much into cords and wires when you could upgrade a component.
Having said that, if you want to upgrade your system sooner vs later... I would recommend a power conditioner now... then stop and save up for... a better preamp... which you would plug into the power conditioner and only use the amp portion of your integrated. Then as money permits upgrade other components.
If you simply want to get the very best performance out of what you have, then power conditioner and power cords. I found inexpensive ~<$200-300 are not generally worth it. Try used... used cables dot com. The integrated will get a pretty good boost from a good high amp cord. sThe rest of your equipment... not sure. You may have to try it to find out.