If you have a speaker that drops down to 2.5 ohms, with an 8 foot speaker cable, going from 18awg to 10awg will increase the level, at that impedance valley, 0.3db, and the damping will go from 24 to 150. Audible? Maybe. If your speaker only drops to 4 ohms, those numbers are 0.2db and 40 to 250. Audible? Probably not. Those impedance valleys almost always happen at bass frequencies. This is a change from 18awg to 10awg, so a pretty severe change. Small gauge changes will have smaller differences.
How many watts or amps you are pushing out it not the relevant metric. The lowest impedance of your speaker is, though lower impedance means more amps at the same voltage.