You can also bypass the front panel power switch by directly pressing a tiny power button on motherboard.  #2 power button (POWER_BTN)
I have an old reliable XPS 630i .  power surge a week ago while it was in sleep mode.  sleep mode light on on/off switch blinking but it would not power up.  after cutting power it will not power up.  Did a PSU test on the back and the power supply and everything else lights up and fan runs.  Is the next step to replace the power switch? .. any tricks to removing that front cover to get at the power switch ??
XPS 630i, power up issues