Swap out X51 CPU?

Hi all,

Couple of questions. Firstly - does the base model x51 with the Ivy Bridge i5 and GT545 have a lower wattage power brick than the more expensive i7 and GTX660 model? OR do they all use the same brick?

Secondly - is it possible to buy the cheaper i5 model then put an i7 CPU in it? I know it's the same socket - but will the cooling be adequate?

Thanks for any info! :)