|You're very lucky you didn't fry any other components. The PSU is the most important piece of hardware in the system...also the most overlooked.|
"How many watts should I look for?"
400W or better.
"How many 12v rails?"
"How much amperage on rails?"
At least 30A on the +12v. +3.3v & +5v should be less than 30A. Here's a
cheap low cost Corsair 400W: