Not sure but watts dosent really matter to be honest, okay the do to a certain extent.
Its all about speaker/sub placement and the structure of the venue.
Say in Room2(the bar) at ministry of sound there is quite abit of reverb at times because its a very 'open' area where as room 1(room with stage) is a square room with speakers in each corner which all point towards the centre of the dancefloor which sounds fucking sick!
But yeah the soundsystem in Room2 at matter is bass heavy and fucks your ears up if you are standing next to one of the speakers stacks.
Any frequency sound will damage your hearing. You just notice bass less, as our ears are less sensitive to it.
This is also why hearing damage from bass goes relatively unnoticed - if hi/mid sounds are too loud, we turn down the volume, but our ears are less sensitive to low frequencies, so we may be doing damage, and not realise it.
When you get hearing damage, loss of bass perception is usually not noticed due to its subtlety, and our ear's insensitivity to it. In any case, most adults can't hear low bass frequencies well anyway, but they do physically feel it, which "makes up" for it.