interconnect suggests under 300 used.

I just spent my allowance on upgrading my system. What is left are cables suggested by the forum. My budget is spent so would like the best cable available for under $300 used (1m pair/xlr)with all mark levinson equipment and electrostatic speakers. I am using monster cables now.I have not received the ML390 yet but the cables i am using are medium grade monster IC with RCA connections. If I can afford a better cable if going with a rca connections should I?