Worth the effort? Cabling inside sub

Just a caution about the wires from the RCA’s - they look like PTFE (teflon).

When PTFE is heated to soldering temperatures, it begins to decompose, and the decomposition products include one of the most dangerous gasses known, HF. If those wires really are PTFE, best to avoid messing with them.

There are very few things as slippery as PTFE, but cross-linked polyester, which is also used in quality audio cables, is similar. If they are slippery like PTFE or cross-linked polyester, you probably shouldn’t chance it for safety reasons. And you can’t buy better wires anyway.

Suggest that if they are real slippery, don’t change them.

For short runs of line level signal, especially low frequency, the main thing you are hearing is insulation (the physical phenomenon is called dielectric absorption, or DA). PTFE and cross-linked polyester are the best conventional alternative (only air and vacuum are better).

There are safe ways to solder around PTFE, but they involve things like:
- fume hoods with high volume exhaust;
- respirators;
- gloves;
- soldering at eye level so hot gasses flow up and away from the face;
- low temperature solders;
- precision soldering equipment run at the lowest feasible temperature;
- and absolutely not fiddling while you hover over something, while you try to remove a connection that someone else made, which may involve high temp solder or a good mechanical connection.

People do tend to recover from HF burns, but they are insidious. HF burns tend to show up after a number of hours, and get worse for a day or two. You can read all about it in MSDS. Best to avoid.

And also, I agree with everything  @almarg  wrote. Leave the RCA wires alone.