Not sure why you would want such a big speaker wire ? 18 gauge wire with 8 ohm speakers would equal about 800 watts of power.. 18 gauge as a rating of about 10 amps.. 22 gauge can still provide 5 amps and nearly 200 watts of power. The amp used for your speakers is a TDA2030, it :

Typically it provides 14 W output power (d = 0.5%) at 14 V/4 Ω. At ±14 V or 28 V, the guaranteed output power is 12 W on a 4 Ω load and 8 W on an 8 Ω (DIN45500).

So a speaker can draw a maximum of 12-14 Watts, and you want to use a 800w cable ? There is absolutely nothing wrong with using 22 gauge wires to wire such small speakers, and no gain except toughness of the cable to use such a big wire. Plus , 12-14 watts would mean you're driving the speakers at the maximum volume , all the time , and there is a constant sound playing non stop to generate the full 14 watts.. Your cables are probably pulling about 5-6 watts at the most during a normal game..

Of course , there is nothing really wrong with using such a big wire , but it's really not necessary.