To answer your first question... If you've found interconnects you like, then it makes perfect sense to try the same company's speaker cables (and power cords too, for that matter). Depending on the system, you can sometimes get very good or even better results mixing different company's products, but of course that will involve a higher degree of trial and error.
Second question: Simple answer, yes, they can sound very different.
Second question: Simple answer, yes, they can sound very different.