Looking to Upgrade [MOBO/CPU]

Hey, thanks for reading.

I'm currently looking to upgrade my computer. I currently own a pre-made computer, if my memory is correct, that I bought at BestBuy around 3 / 4 years ago. Here is the link to the specs of the computer.
The reason why I'm looking to upgrade my computer is because I think my mobo does not properly support the GPU that I have currently and it is bottle-necking.

http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&dlc=en&docname=c02481318#N90

I've added a few things between buying it and posting this thread.

EVGA SuperClocked 02G-P4-2662-KR GeForce GTX 660 2GB 192-bit GDDR5 PCI Express 3.0 x16 HDCP Ready SLI Support Video Card
and
CORSAIR Enthusiast Series TX750 V2 750W ATX12V v2.31/ EPS12V v2.92 80 PLUS BRONZE Certified Active PFC High Performance Power Supply (Not sure if its the exact one, but same Wattage)

What I'm looking to upgrade is the processor, which in turn I need to upgrade the motherboard. I'm not the best expert on computers so I need some help with the upgrade.
I don't care about the companies that the products are from, I only care about the best buy I can get within my budget.

I currently am willing to spend around $400. A little bit above or below is fine.
Whatever you recommend I should buy, even if it exceeds my stated budget, will be fine too.

 

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=8216867&Sku=M69-7175

Looks like it may be near perfect for you. Just don't forget to grab a aftermarket CPU cooler, as the stock cooler is a joke.

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=7413643&Sku=C13-2101 Is considerd the king of cooling, though if you don't plan on overclocking;

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=6046364&Sku=T925-3046

 

Do you need it for gaming? If so i would advice you to get around $800-900 and then you could build a really nice PC for this money.

 

definitely recommend you leave your pre built for backup or you could turn it into a router. Sometimes the operating system is locked down to certain components so you might screw yourself with a upgrade. You can build a new machine with $400 if you know how to shop and you won't get stuck with a generic mobo/psu like you would from buying from hp. Will cost you an extra $100 if you wanna buy windows. You don't need to buy a dvd drive because you can install os from flash drive. It's year 2013, computer components are at an all time low, excluding ram which has raised in price recently. Now is a great time to buy too considering you can get a gtx $760 for $250.