Want to replace my speaker cables

See my system. I suspect that my speakers cables are my weak spot. I need about a 15 foot run because all the gear is on the right side of the room. I bought the Nordost years back primarily because it seemed it was OK, and even more importantly, it was flat so I could put it under an area rug. I still need a relatively flat cable as running under the floor isn't an option.

I'm not in the bright/hyper detail camp. Prefer warm, full, solid bass and midrange glow.

Maybe I should just keep my cables?

Suggestions please?