You can argue however you like about being a believer or not, but I would certainly wager that dollar for dollar, the value you get out of monster cables is ridiculously low. That is to say, if I have 100-200 dollars to spend, I will get much better sound improvement by investing it into other parts of the system and spending 10-15 bucks for a quality 16 gauge oxygen free speaker wire from Lowe. I would go even further to say that this rule of thumb will hold true until your system is worth well over $5,000. At this point, well, if you have to worry about blowing an extra couple of hundred, then you probably shouldn't have that setup in the first place.
Another interesting point though is that I have heard that it can make a significant difference by having a quality interconnecting system. Apparently, if your contacts at the reciever or speaker are poor, you can have sparking which will manifest itself as small popping in the sound. Haven't had much of a chance to verify this phenomenon or examine just how good is good enough, but it seems to make sense anyway.
My .25 cents....(inflation and all)
J