That's a pretty nice mid-end gaming machine.
You linked the memory wrong.
It's is highly recommended that you don't use the power supply included with the case. I would suggest a reliable brand, such as:
Newegg.com - FSP Group (Fortron Source) AX400-PN ATX12V 400W Power Supply 120/220 - 240v NEMKO, TUV, CSA, IEC, UL, CE - Retail
You should get past 3GHz, easy, no sweat.