I've built about 20+ computers now and I've only had a power supply blow once. When I opened the case there was bits of glass all over the inside, the glass fuse in the power supply had blown, fortunatly nothing else was damaged and I just replaced it. It is possible you've just had very bad luck with 2 power supplies going but I would say its very unusual for this to happen. I would be looking for a replacement system or a refund personally because there could be something else wrong and you have no way of telling.
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