Lan:
The Antec PSU's have 2 fans, a "puller" and a "pusher". The puller pulls air into the unit and is inside the case, the pusher exhausts warm air to the world - global warming. Normally the puller runs all the time, the pusher when the PSU internally detects heat problems. This arrangement keeps the noise levels down.
The "puller" is quite a hefty piece of kit. When pressing the button, it at most twitches, or turns maybe 1/4 round - never more.
When I had the older Sparkle PSU in there, the single fan started and stopped within a second.
The CPU fan is an altogether lighter affair, and varies between a "substantial twitch" to a "yee-ha" spin lasting perhaps a second, before chugging to a sighing halt. This could easily be capacitors holding enough charge to hold the rail up, or the generic lightness of the fan allowing a certain amount of variability.
Viz the switch, I can try pulling the leads off the head and shorting the pins with a bit of wire. I have yet to try this, but my wife is looking at 1) the dining room table covered with semi-disassembled machines, and 2) the steaming pot of chilli I am preparing, and making hungry "feed me" noises. This will have to wait until the morning.
I wish I had a job, a paying job I mean.