I use magnet wire, the Vampire CCC stuff, for everything. Even the cryoed stuff isn't expensive, and the non cryoed wire is dirt cheap. One has to be careful while braiding, and unkink the little kinks, but with practise it all comes fairly easy. I hear no difference to the super expensive wires/cables I used to use, Cardas and Coincident.
Frank is right, it is all in series, signal wires/cables, crossover leads/internals, and voice coils. Has anyone ever given it a thought when soldering that large 10 or 12 ga. wire to a woofer, only to see that relatively small wire on the woofer, "hm, is this big cable a bit of overkill here as it ends up in this little wire?"