PSU Question

[Leezy]

Hi all, might be a very dumb ass question but are there different size PSU's for small cases/big cases and/or Micro/normal Atx?

I got a micro ATX comp and im thinking of getting a 7600gt as it only has onboard graphics atm, but its only running a 250 watt PSU and i think i need a lot more to run the card can any old PSU fit?

thanks

 

[Leezy]

oh and what do you rekon will be enough to run a 7600GT card?

thanks