The net effect of increased rail voltages is the ability to produce higher peak SPL. Watts are the product of voltage and current. Amplifiers are voltage amplifiers. The driver effectively determines the demand for current via its impedance.

If you were to compare two amplifiers that were able to deliver 2400W into 4 ohms, with one of them having the ability to deliver higher voltage but unable to deliver the current to exceed 2400W (ie limited to 15A of current delivery, but able to deliver 160V) and the other one having the ability to deliver more current but not the ability to deliver enough voltage to exceed 2400W, (ie limited to 97V but able to deliver 24A) the one with the higher voltage capacity would be able to deliver more power, and therefor more SPL, everywhere above 4 ohms. The one with the higher current capacity would be able to deliver more power below 4 ohms, but excess capacity in those ranges isn't always useful because that’s where it needs to be limited to protect voice coils.

Thus more voltage results in higher SPL capability at all frequencies that are outside the range limited by current demand.

Bottom line, higher rail voltages are generally better for music.  Higher rail voltage provides increased dynamic headroom, enabling the amplifier to produce louder sounds without clipping, allowing for better handling of dynamic peaks in music, providing clearer and more detailed audio reproduction.