At 100 000 A for a 100 MW data center at 1000 V, speaker wire is a joke.
You obviously need at least a dozen stands in parallel!!
Clearly skin effect scales with frequency but, 400 Hz is still low, only 2.5x lines frequency (the scale is by the root); so the skin depth is 3mm. 3mm on each side makes for a pretty hefty rectangular cross-section.
If you could get that 100,000Amps flowing through your speaker wire, the vaporised copper and the plasma channel would probably keep your 100MW flowing, at least until your building caught fire.