$500-$600 Multimedia PC, need parts help.

I'm pretty new to homebuilding and would appreciate some help getting started on parts.   Thanks.

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APPROXIMATE PURCHASE DATE: Within the next month. The sooner the better, haha.

BUDGET RANGE: $500 - $600 Before rebates. I'm willing to go slightly higher (e.g. 50 dollars or so.), though I suppose the lower the better.

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: Media/Movies, Gaming, Music (I use Sony ACID; I'd like to be able to play through my computer, though if too expensive I'll just purchase a mic.)

PARTS NOT REQUIRED: Keyboard, Mouse, and Monitor are not required, though I would like suggestions on a decent speaker system.

PREFERRED WEBSITE(S) FOR PARTS: newegg.com, possibly eBay.

COUNTRY OF ORIGIN: United States

PARTS PREFERENCES: I don't have any particular preferences. Though I'm having trouble deciding on a processor. A friend of mine swears by AMD, but I've been hearing some good reviews on Intel's i-series chips. Also, I'm thinking 6 GB of RAM and a 1 TB Hard drive. I like knowing I have the space, even if I won't use it immediately.

OVERCLOCKING: Maybe...I honestly don't know too much about overclocking.

SLI OR CROSSFIRE: Is it absolutely necessary to run two graphics cards?

MONITOR RESOLUTION: Most likely a 17'' (1280 x 1024?)

ADDITIONAL COMMENTS: This will be my first homebuilt PC, though I'll have help. The new semester for university starts in the fall, and I'd like to have this as my reliable desktop. I have an old Macbook that I'm keeping solely for portability and video editing...but if this PC can handle that too, fantastic! I'm an avid gamer, as well. It doesn't need to be able to run Crysis on full settings or anything, but you know enough so that I don't have 9 FPS all the time.

As I said before, I'd like to be able to run my keyboard and/or my bass directly into the computer as well as a wacom tablet.

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Thank you all in advance for helping. I'm doing my research to the best of my ability but, having a community to ask questions directly to is much easier. If I need to provide anymore information, let me know!