i've been putting on warehouse parties for 25 years. we have one this saturday (anybody in sydney, pm for the details).
here's the deal. you need a lot of sound and it has to be good quality sound. there's no point in playing great records if you don't have a good sound system. you look like a fool and nobody has a good time.
you need 4 point sound. that is, a bass bin and tops in four corners. The easiest solution - just order a four point Function One sound system. the aim of the four point sound is that no one is ever very far from a speaker when they are on the dancefloor - it sounds rich and full wherever they're dancing. rather than just sounding good for the two metres in front of two speakers.
never ever use powered speakers. they are only suitable for bingo halls and have a very harsh sound that cannot be pushed.
remember, if you push a system into the red, because you didn't get enough sound in the first place, it's only makes the sound worse.
the point is not to have a sound system so people can hear the music, they need to be able to FEEL the music. and that takes big bass bins. put all your money and effort into getting the best and biggest sound system you can.
every famous club in the world was also famous for their sound system.