Guys, don't blindly follow the masses. AMD64 is a superior CPU to Intel, yes, but for music and video encoding or CPU-intensive calculations (see SuperPI), Intel outperforms its competitor. For what he's said his rig is going to do, I'd suggest an Intel 3.0GHz or higher Prescott CPU, 512MB of Dual-Channel DDR2 RAM, a 925X chipset LGA775 motherboard, an ATI X850XT PE from Buy.com for about $460 shipped (ATI outperforms NVIDIA due to its sheer power in any benchmark that doesn't have "Doom 3" in the title). ATI will come out with SLI for ATI cards within the next few months, so go ATI instead of NVIDIA. For a sound card, I recommend Sound Blaster Audigy 2 ZS Platinum if you need inputs. I am a Creative Labs fan, so there may be other comparable or better sound cards out there, but I don't have experience with them, so if you have something else in mind, by all means. Your PSU ought to be a quality name-brand product -- same goes for the case. Both are a matter of brand and aesthetic preference. 120mm fans are quieter than 80mm fans while producing the same cooling output if quietness is your cup of tea. Alternatively, you can use a fan controller from Vantec, Zalman, or Cooler Master to name a few brands. The NEC ND-3500A is a good choice for an optical drive if you plan on burning double-layer media. I'd suggest a WD Raptor or two in RAID 0 for insane performance coupled with a Maxtor DiamondMax 10 200GB, 250GB, or 300GB SATA Hard Drive with a 16MB cache for storage. You can skip the Raptors if you're strapped for cash. Floppy disk is optional, though I would suggest it (necessary for enabling RAID on your hard drives and c'mon, it's $10). Oh, and you're gonna want Arctic Silver 5 Thermal Grease. Good heatsinks for your CPU include the Thermalright XP-90 or XP-120 or a Zalman Copper or Copper/Aluminium heatsink. Don't cheese on the heatsink, though, 'cause Prescotts run hot!
Your use for the computer is almost the only advantageous sector that Intel has, and Intel pwnz AMD in encoding, so if that's the bulk of your intent with the PC, then go for it. Additionally, PCI-e is readily available for Intel CPUs.
Good luck.