I have, in a pinch, used mic/signal XLR cables to connect powered speakers and with 25Watts and car speakers you will probably get away with it, but as Caleb said, you need (much) thicker cables for speakers.
XLR is not used for speaker cable much anymore. Better option would be to use SpeakOn connectors. A) you won’t confuse your speaker and signal cables and B) they are much easier to attach to the thicker speaker cable.
Finally, but that is just me, you can probably find a pair of 10″ used active PA speakers that are way more efficient and better sounding and also built for the road and the kind of use you will put them through for a price not much higher than a decent amp.
So, depending on your reason to do this, that might be the wiser decision. It will most certainly look more “professional”.
Hope that helps. Just my two cents as usual.
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