everyone has an opinion, I feel upgrading your cables is one of the easiest and cheapest ways to upgrade your system. I would buy cables on Agon try them out and sell them if you do not like them. If you use the Cable Co you will end up paying full price for something that could be had on Agon for about 1/2 price, otherwise they are terrific.
Cable has come a long way since the 80s.
I recommend Alpha Core Goertz MI2 Veracity as the best cable in the $200 price range, another good choice is Kimber 8TC which is a good all around cable but the Goertz is lively with better tone IMO. I bet you would find either is much better than the Monster cable.