What would be the best graphics card

[EpicLord9]

My specs are:

Operating System
MS Windows 7 Home Premium 64-bit SP1
CPU
AMD Phenom II X2 521 30 °C
Callisto 45nm Technology
RAM
4.00 GB Single-Channel DDR3 @ 666MHz (9-9-9-24)
Motherboard
FOXCONN 2AB1 (CPU 1) 37 °C
Graphics
HP 2011 (1600x900@60Hz)
ATI Radeon HD 4200
Hard Drives
977GB Hitachi Hitachi HDS721010CLA332 SATA Disk Device (SATA)

And I REALLY want to upgrade from my 4200 or even overclock.
I've been thinking about these cards:

PNY - GeForce GT 430 1GB DDR3 PCI Express Graphics Card
http://www.bestbuy.com/site/PNY+-+GeForce+GT+430+1GB+DDR3+PCI+Express+Graphics+Card/2265044.p?id=1218317314615&skuId=2265044&cmp=RMX&ky=1whxm51gbOgORrn6M8JOUlLjDtR0yY7Rx

PNY - NVIDIA GeForce GT 520 1GB GDDR3 PCI Express Graphics Card
http://www.bestbuy.com/site/PNY+-+NVIDIA+GeForce+GT+520+1GB+GDDR3+PCI+Express+Graphics+Card/2869502.p?id=1218361287065&skuId=2869502&cmp=RMX&ky=1whxm51gbOgORrn6M8JOUlLjDtR0yY7Rx

VisionTek - ATI Radeon HD 5450 2GB DDR3 PCI Express Graphics Card
http://www.bestbuy.com/site/VisionTek+-+ATI+Radeon+HD+5450+2GB+DDR3+PCI+Express+Graphics+Card/2286098.p?id=1218318237077&skuId=2286098&cmp=RMX&ky=1whxm51gbOgORrn6M8JOUlLjDtR0yY7Rx

MSI R5770 Hawk Radeon HD 5770 1GB 128-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127490&cm_re=5770-_-14-127-490-_-Product

Or anything else that you guys recommend, the card has to be $100-$200
I want to have a card that easily plays source engine games, and Oblivion, and could possibly meet borderline with BF3/BFBC2
and if I could just overclock and play Oblivion and source games please tell me how.

The computer itself is the: HP Black Pavilion p6823wb Desktop

 

[IH8U]

This would probably be your best bet, especially since I can't find the wattage/amperage for your PSU:

http://www.newegg.com/Product/Product.aspx?Item=N82E16814150540
$110 XFX HD-677X-ZNLC Radeon HD 6770 1GB 128-bit GDDR5 PCI Express 2.1 x16

Another worthwile thing to add/Replace is your RAM:

http://www.newegg.com/Product/Product.aspx?Item=N82E16820231422
$42 G.SKILL Value Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333

Eventually you can also replace the CPU.
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103993
AMD Phenom II X4 830 Deneb 2.8GHz 4 x 512KB L2 Cache 6MB L3 Cache Socket AM3 95W Quad-Core (OEM, so you'd have to re-use your HSF)

 

[jyjjy]

Why would he need more/different ram?
For now you will need a new power supply along with the card. If you have $200 to spend then this is what I would get these;
http://us.ncix.com/products/?sku=55409&vpn=N460GTX%20HAWK&manufacture=MSI%2FMicroStar&promoid=1339
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371030
That would total $185 before rebates, $150 after. They are both on sale at very good prices so get them before the sales are over. You'll be able to play all current games at fairly high settings at up to 1080p.
FYI your current processor is actually an Athlon II x2(lacks L3 cache) despite the name. It has a high clock speed which is nice so it should be passable for now but to get the most out of the card I linked consider upgrading to a Phenom II x4 when you can afford it.