I first explored replacing internal wiring in Ed Long Sonex MkII Time Alignment speakers waaaaaay back in the late 1970s. At that time they were already older speakers, meaning the internal wiring was not on the hifi radar. I replaced it with Wire World's first gen internal wiring, and painted the insides with many coats of boro-silicate. Due to the tall cabinet, I horizontally inserted a long threaded rod to alter any resonance, and finished the job hanging some wool over the rod. Well worth it
These days, unless you own tube gear there isn’t a lot to be changed, but I found Oppo 105 wire upgrades on EBaye. First, I replaced the OEM IEC with a Furutec long silver tail to connect to the OEM power supply board, fuse jumper, and 110/220 switch. The improvement was not subtle, so I replaced the OEM PS with an aftermarket LPM to excellent results, though eventually I did get a active preamp
My Emerald Physics 3.4 speakers have outboard XOs and came with cheap jumper wire. I ordered WireWorlds newest internal wire but it took a couple weeks to get it. As soon as I made the swap, my first thought was this speaker could have easily sold for an extra $1-2,000
I think DHLabs sells bulk wire
hth