Once the signal is more complex than a sine wave things get crazy. The more frequencies in a signal, the harder it is to model the power draw since different parts of a complex curve cause the speaker to act more like the low resistance inductor it actually is. Discontinuities and areas of constant voltage (both caused by clipping) are the worst, and to make things even more fun the amplifier is part of the system and affects things as well.

But assuming you know a lot about the speaker, the amplifier and the DAC you could probably build a model that works well for simple sinusoidal audio, but that doesn't cause problems anyway. All bets are off for anything more complex.

So instead you're left with a few options: buy reasonable gear and don't play crap audio, play crap audio but massively overbuild your system so you lower the risk of getting into the unknowable danger zone that changes depending on what you're playing, or use a bunch of heuristics on a signal and try to distort it in some way so it's less potentially damaging.

The problem with the latter is since you don't know where the line is it's easy to be overzealous and end up distorting lots of stuff you don't need to. Problem with the middle is you either end up with something much larger and more expensive than you need, or you cripple what you have to give you a wider margin of safety. Problem with the first is apps like VLC make it exceptionally easy to accidentally play crap audio. Pick your poison.

Could Dell spend a couple extra bucks for higher quality components and create a wider margin of safety? Probably yes. But at the same time the VLC developers are being reckless by putting a tool into consumers hands that makes it so easy to play potentially damaging audio signals.

Edit: clarifications