Well,
A) More expensive S-Video Cables are irrelevent. I just discovered recently that it's all in what type of cable it is. If it has only on plug for a particular system, then most cables should retain relative parity. However, if it's one of those three-in-one doohickeys, you're in for a world of pain (or lowered quality)
B) Thickness of the wire for the audio and video equipment in question is a matter of looks and EM shielding. Unless you have a perpetual EM storm floating behind your TV, or some gigantic Power Inverter back there, thinner, cheaper cables should work just fine.
C) In audio equipment, distance is the determinant of audio quality. For long distances, you will need some thicker wire, but more often than not, 16 gauge wire will sound exactly the same. Anyone who says otherwise, I hold into that special category of "audiophile" who believes they can tell the difference between an $800 receiver and a $900 receiver.