Need advice on new GPU, possibly CPU

Hey guys i was just wondering whats the difference between DDR2 and DDR3

also whats a Radeon HD 5450 (Cedar)
is it the same as regualr HD 5450?

For difference between DDR2 and DDR3 go through these links:

http://www.artipot.com/articles/210869/difference-between-sd-ddr-ddr2-and-ddr3-ram-explained.htm
http://www.anandtech.com/show/2232

The "Cedar" chip powers ATI's bottom tier cards. All the 5450s are part of the "Cedar" family.

so...... does that mean it's good or bad?

What?

DDR3 is definitely the way to go now if you're building a new system.

As for the "Cedar" family of ATI cards, they're not really meant for high-end gaming. Neither is "Redwood"(HD 5500 and 5600 Series). "Juniper"(HD 57xx), "Cypress"(HD 58xx) and "Hemlock"(HD 5970) are more geared towards gaming.

So yes actually they are sort of "bad" you could say.

Ok i have now about $650-700 to spend im planning to buy a new system and upgrade the psu and gpu.
The pc i want to buy is this one
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=6089231&CatId=5138

Is this a good choice and if it is what gpu/psu should i buy?

If possible, I would refrain from wasting so much money on RAM.
Otherwise, yeah its pretty decent.
What you would want is
SAPPHIRE 100297L Radeon HD 5830 1GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card w/ ATI Eyefinity Technology
CORSAIR CMPSU-550VX 550W ATX12V V2.2 SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply.

from your advice its about $800

whats the difference between the corsair psu and this one
http://www.newegg.com/Product/Product.aspx?Item=N82E16817170010

and can you tell me whats the difference between this
http://www.newegg.com/Product/Product.aspx?Item=N82E16814161327
and this
http://www.newegg.com/Product/Product.aspx?Item=N82E16814161325

The difference between the corsair and the powersupply you posted is that the one you posted sucks.
There isn't much a difference between the two graphics cards.

XFX HD-577X-ZNFC Radeon HD 5770 1GB 128-bit DDR5 PCI Express 2.0 x16 HDCP Ready CrossFireX Support Video Card
CORSAIR CMPSU-450VX 450W ATX12V V2.2 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply

Guess I did my math wrong. Its a tiny over, but if you really need you can step down to a 5750.

Can you tell me what do you mean when you said it sucks?

I mean its not very good.

EDIT: I'm condescending sometimes eh?
The company that makes it is ambiguous, most likely a small Chinese manufacturer which means highly unreliable build quality.
While it claims to have 25 amperes, I find it unlikely to have more than ≈ 15 reliably.
You get what you pay for.

ahh....i see is antec a good company?

Sure, but my recommendations above still stand.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817371031

is this psu good? if not ill just get corsair

Fine, but the corsair is cheaper.

It's about the same after the promo code

I guess im pretty much set

Question:can the pc run MW2 and WaW at maxed out settings?

The HD 5770 / HD 5830 should run those games at max settings.

I currently have that PSU and its pretty solid granted I've only been using it for less then a month and got it for $40's during a shell shocker deal. Just note it won't come with any instructions or power cord, and it can be a pain to do cable management with it if you don't have a large case.