jonnyGURU.coms review of the XION 700W PSU said that it is based on an old inefficient design with no PFC and has horrible voltage regulation.
They don't use high quality capacitors (i.e. they use CEC International Holdings). The schottky barrier rectifiers for the +12V rail are 10 Amps in rating away from disaster (i.e. too under spec'd).
Would I be surprised that it self-destructed? Not really. It may very well have been the rectifiers for the +12V rail that blew.
The next power supply unit you purchase should be from a reputable brand like Antec, Corsair, Enermax, Seasonic.