Does PSU have to be 2.03 ATX?

[Sanwa]

I have a 300W Sparkle Power Supply that's not that old, but I believe is ATX 2.01. I have a 1.4 Athlon but don't plan to overclock. Will I be ok? What will be my first clue something's wrong (i.e. will the +5V rail start to drop)?

Thanx