Hey all.. i really need a new head unit.. i was looking into the premier p740mp, but for $50 less i can get the 640.. the only differences that i can see is that the 740 has 4 volt pre outs and the 640 has 2 volt.. also, the 740 plays mp3.. question one is.. does the 640 have 3 pre outs our just 2? if it has 3, then i qould probabil go with that one.. i can live wth just 2 volt outs.. my p4400 only has 2 volt, and it sunds very good.. Also, do all pioneers fit in the same cage? I dont want to have to buy another. Is the 740 worth the extra $50?