Good wires will increase the signal flow and also allow for more power..If you are running a SQ system or a high power system you will notice but not a big difference. I personally use 12-14AWG to allow for both and room for growth.
No matter what calibur sound system you have bigger gauge speaker cables will make a very noticeable difference. If you are running like 20 gauge for your subs and you switch to 12 gauge(recommended for any sub) you will notice much better bass. The same holds true for home stereo. Use a beefier gauge wire on your home stereo speakers and notice how your bass response goes up. Low frequencies(bass) are the hardest to reproduce. So when you increase your signal flow with bigger gauge wire that is the biggest improvement you will notice.