You won't really notice a difference by switching to a larger wire alone.

If you're using an aftermarket high voltage capacitive discharge ignition system, or you have problems with engine heat melting the jacket on your wires, I could understand switching to a larger, more heavy duty wire. Most companies have some sort of gimmick to get you to buy their wires. However, I ran an MSD 6A ignition and Blaster 2 external coil with factory Honda plug wires and never had any problems.