Better cable does make some difference.. improvement but also, its up to the "buyer beware" as some people expectation is way out of proportion.. If you upgrading from a RM10 to a RM100, its a bit hard to justify 90% increase in quality as you paying 90% more (pardon the math)
Also, not all people have that much money to spend.. so still back to "Buyer Beware"
I have not used Monster S-Video but experience on other "branded" S-Video do have improvement. (Tested Siltech & Used Audioquest & Black Rhodium) I won't say Monster is not good (Pricy - Yes) as I am also using some... but its expectation.. If you have the budget.. then go ahead... If not... the best way is to try to borrow one from friend to test (If Friend have and willing to borrow or got spare to lend).