1) Your front L+R pair are the most important; 75% of the signal comes through them. I'd suggest at least half your budget here; these are the linchpin and matter the most. You use these for everything, all the time, no matter what, so most of your focus needs to be here. As your budget gets higher and you've got the basics covered, the percentage put here should climb. An excellent L+R pair can carry a weak system, but no amount of money and gear can fix bad front speakers.If you assemble your system in that order, you'll get the most immediate enjoyment, and can cherry pick components and steadily enhance/upgrade the system over time, so you get to enjoy the same stuff over and over as you add new pieces. :)
2) Then you have to have a receiver to drive them. Your electronics don't need to be enormously expensive; the little Panasonic digital receivers (XR-series) are in the $200 to $250 range and are just fine for driving $2k speakers. Low-end Onkyo units like the 504 are also an excellent choice.
3) The sub is next most important, assuming you don't have full-range L/R. The sub will fill in the sound and give your system punch and power; it will improve the immersion a bunch, especially if you have a good one. If you can get up into the $300-$400 range, that's the sweet spot for performance. You can spend a lot more money and get a beast, but you'll usually get max boom-per-buck at around $400.
4) The center will enhance movies a lot; up until now, you've been spending on both music and movies, but now you're adding stuff just for movie-watching. Centers need to have very good dialogue reproduction and almost nothing else. Ideally, get something that's a reasonably close timbre match to your L+R pair. The center is the anchor for movies; you can use a 'phantom' center just fine with good left and right speakers, but an excellent center will improve realism a bunch.
5. Finally, add your satellites. These can be cheap and crappy, relatively speaking, unless you are doing a lot of multichannel music. For movies, they mostly just do ambient sound and aren't that important. They add space and air, but they don't actually do that much and don't need to be that great.
posted by deadfather at 6:57 PM on March 21, 2007