How many come with the antec nine hundred?
Two 120mm fans in the front, One 120mm in the back and a huge 200mm fan on the top of the case.
Yeah you can add another fan or two on the side panel with the optional fan mount that comes with the case.
You can cut a hole in the bottom of the case for the psu ventilation.
Ya a modular psu is suggested for that case but a normal psu will do, ive seen em with the same psu as I got in the Antec 900 and there was no problem and this psu has very long cables.