jorge, it sounds like you have a good start on things.
The 4 M3s all around for music would be very nice. Because they are smallish in size most ppl would recommend a sub but you can decide if you want one at a later date. There is no rush. However it would help to fill in some of the low end for music and certainly more boom for movies. Even a small sub is better than none at all and volumes are always adjustable.
As for costs, take a look at the Factory Outlet offerings that Axiom has. You can save 10% on the speakers which helps to open up the pocket for maybe slighter higher featured electronics or savings for other components.
Harmon Kardon, Yamaha, Denon, Onkyo, NAD, Pioneer are all good names that sell cd players, dvd players, receivers, etc., in various price levels for your choosing. Stick to your budget unless you know you can afford the debt. Do not let anyone convince you of the features that you need. That being said, for modern dvds, getting a receiver that is capable of Dolby Digital or DTS 5.1 playback should be on the features required list. Most do have it now days, even receivers that cost $100 or less.
