For video cables and coax for sat/cable TV/antennas, yes, there is obvious difference to all sighted, unbiased people. At a certain price point the difference may not be visible to some, or may simply not be worth the price. Note that ALL video cables should be coax.

Monster Cable is overpriced. Some good choices are...
bettercables.com
rhinocables.com
kustomkables.com
wickedcables.com
catcables.com
avcable.com
do-it-yourself


Audio cable is a different story. It's a tough call here, but you can get 12 AWG speaker cable very cheap and please both sides of the arguments. Or make your own with CAT5 cable even cheaper. (8 wire CAT5=15 AWG) For interconnects, stranded versions of the above video cables would be good. Coax is not necessary, however. You need to shop carefully.