Cables make about as much difference as subtle EQ. I pretty much agree with 909's response, except I think it's too safe, I'd go just a bit further -- the response applies to most cables, but if one were to compare, for example, the most extremely bright cables with the darkest, I think the differences would be audibly different. For example, my Pure Silver Sound Quartets are audibly superior in the upper frequency band to most every other interconnect I've tried...in my system. I need to track down a pair of balanced silver interconnects for cheap. It doesn't have the midrange to die for that my Cardas Neutral Refs do, but it's got more air and detail than anything else I have by far.
Still my favourite response: