How old was the PSU? I've popped a few myself. They can go with a hell of a bang/flash (which is what it sounds like happened to you), or they can go quietly and the capacitors just melt and start leaking gunk (a good reason to have bottom mounted PSUs - amongst others).
When decent ones pop (and Antec are one of the better makes around) it's usually the result of old age, extreme heat (usually caused by dust build up), a massive power surge (I have pretty hefty surge protection system in place for my more expensive hardware to rule this out), or someone getting a bit too giddy with an overclock
The other thing with decent PSUs is that if they do pop, they have built in surge protectors to protect the rest of your hardware. The chances are you won't even have damaged sectors on your HDD (though you may have lost some data if it was reading/writing at the time).