Some of the GameXstreams used an FSP unit back from when they were good - not the Epsilon variant - I have one it has decent ripple, etc. stats. However pretty much all of them have a lifespan of about 10 years max before the capacitors are done (so regardless I'd get it replaced). Not 100% but I think some of the later ones used a CWT unit that was pure junk - in other PSUs its been known to take out hardware. The StealthXtreme variant would literally lose about 100 watt a year off its max capabilities :s
That said the symptoms don't really sound like traditional failing of those PSUs - normally you'd get it randomly turning off under load for awhile before it got to the point of boot failures at which point messing about with USB stuff, etc. wouldn't generally make a difference though could just be coincidental - half a chance it is a motherboard failure.