I have used the similar 4Flat form Nordost and here is my journey:
Nordost 4Flat (2005) -> Signal Cable Silver Reference (2007) -> Clear Day Double Shotguns (2014) -> Inakustik LS-2404 (2020)
There were a few I "tried", that did not make meaningful upgrades and hence returned them. But I suggest that you try to experience them in your system. In a friend's system we tried my Clear Day and Audio Envy cables and the Envy cables were really close to the Clear Days. Mind you, the AEs were not even broken in. So that would be a good upgrade.
Based on what you mentioned, I would suggest to try bi-wiring.