Your new PSU may be a factor in increasing the chances of static discharge. Who knows? The fan design might encourage air to flow over parts generating more energy. However, this SHOULDN'T be an issue because the computer is grounded. But it's possible a change in the airflow could potentiate static charges that are somehow not getting grounded. It could be that your fancy new PSU is hotter and drying out the air in the room... I guess ANYTHING is possible though. I don't think it's very likely that the PSU is the problem.
It's FAR more likely that environmental factors are causing YOU to generate the excess energy. New socks, dry weather, shoes with rubber soles, clothing made of polyester... dozens of factors cause static charges.
Get an EM bracelet, or simply touch a metal object in the room that's grounded, and THEN touch your computer. If the shocks go away, you have your answer.
Increase the humidity in the room, as pointed out by others.
Bare feet don't generate much electricity. Socky feet, and rubber soled shoes will cause you to build up a charge.