I live in Monmouth County New Jersey. And yeah, Ive heard that Newegg is the best. So the size of ram isn't the only thing that's important? What should I know when making choices?
CASE: Generally your choice for aesthetics, however it must have room for all of your parts, and a case with good airflow & cooling is necessary to keep your parts from overheating.
PSU: The Power Supply Unit is powering your entire rig. You don't want to skimp on this part, as a faulty PSU can damage other parts of your computer, and if this dies, your computer won't do anything. There are calculators available to calculate how many Watts your computer will need at full load.
CPU: The brains of your computer. Get a smart computer.
MOBO: The motherboard is the main part you need to check compatibility with other parts. Almost every process runs through the motherboard, almost every part must be connected to the motherboard, everything must be compatible.
GPU: Also known as your videocard, this will control what framerates you get while gaming. The VRAM of the card will affect what resolutions your card will be able to run without 'borrowing' memory from your RAM. 512MB is fine for most resolutions, at 1920x1080+ you might want to consider a 1GB+ card.
MEMORY (RAM): This will be affected most by how many programs you intend to have open at one time, as well as how memory-intensive each of those programs are. For Gaming, as well as having an internet or music up at the same time, (assuming running Vista or Win7) 4GB or 6GB+ is recommended. For photo/video editing, 6GB+ is recommended. Be sure to get compatible RAM. DDR3 RAM is faster than DDR2 RAM (obviously), Triple-Channel is faster than Dual-Channel, but Triple-Channel is only supported by the Core i7 CPU.
HARD DRIVE: How much space do you need? If you need faster read/write speeds; consider buying 2 equally sized hard drives and set them up in a RAID 0 array. Make sure your MOBO supports RAID arrays so you do not need a RAID controller.
DISC DRIVE: Just make sure its a reliable brand, and plays/burns whatever you need (DVDs, Blu-ray, whatever).
Don't get hyped up is a big thing.
I would recommend
This
as your case...
Processor
Hard Drive
RAM Get two of these if you want
Motherboard
Power Supply
Video Card
DVD/Bluray/CD Drive
Total is $765.00.
Just $15 over budget, but if you wanna go a little lower, save money on the case and get
This
You could also swap out that Power Supply for
This (I have it) 
That CPU isn't in stock. I recommend a Phenom II X4 955 for $45 more.
Phenom II X4 955 BLACK EDITION for $190 (vs $145) its core clock is 3.2GHz (vs 2.6GHz on the P2 810 you linked) stock and it overclocks a lot better.
2GB RAM isn't going to cut it either, I'd definitely recommend 4GB RAM. Get DDR2 though, much cheaper than DDR3, and still great.
I recommend this PSU:
OCZ ModXStream Pro 600W It's only $50 after rebate, and its 600W & reliable, just as good as the $70 version whyfly posted.
That's a good
motherboard, but for the Hard Drive I recommend a 32MB Cache instead of 16MB Cache, hard drives are cheap and its a lot faster, drop down to 500GB if you need to.
Did he want a blu-ray player? That thing is like $120 you can get just a CD/DVD Combo for like $30.
