Well, you just said it: I highly disagree with it but yeh If you are looking at something a little sturdier, perhaps look at the Dennon MC6000 as it can be used as a stand alone mixer as well. One thing I don't understand is if you where planning to go with a mixer and use 4 decks, how are you going to control them? Clicking play isn't a very good option, also im not even sure why you need 4 decks to begin with. Sure it's (Nice) but if your just mixing there's no point. To sum it all up, if you want to use a mixer, id wait for the djm 850, as the 900 is quite a blow to the pocket. If you want a controller for the mixer, grab the mc6000, as it can be used without a computer. However personally id just grab an x1 and use that with your 400, as it is a good setup already.