Macs (maybe with the exception of a Mac Pro) are only silent at idle, not in full load. By my definition of 'silent' at least. If you can't hear the system while gaming because you use headphones, sorry, it's not silent.

If you just randomly build a beige box hackintosh, it will be noisy. If you spend some quality time on silentpcreview, you can get one that is silent even under load. I know, I have one.

Still, I'd very much like to get a decent Mac Pro instead. Devil's in the details, let's wait and see. My hackintosh isn't becoming obsolete any time soon.