what to buy under $500 bi wire spkr cable

I had the Monster 2.4, very similar, and before settling on the AQ Oaks, tried the AQ Gibralter. The Gibralter had much fuller, lower, focused bass, lower noise, greater transparentcy, richer mids, more extended highs, etc. Used can be had at your price point. Sounds like a schill right, nope, and I don't have any for sale either.

I doubt it's your cables, and your speakers are capable of good bass so I would look elsewhere.

Discovery Essential

Kimber

Need to know how long a run you need, the price goes up the longer you go.