Need Help on a Budget Gaming PC

[nuke54]

So I'm looking to build my first computer instead of just buying from cyberpower or ibuypower like I have in the past. Only problem is I don't really know that much about mobo's or CPUs, as I've only installed and upgraded RAM , GPU, and a PSU.

Purchase Date: Within the month

Budget Range: 400-500

System Usage: Gaming, Internet, Photoshop

Parts I Already Have:
EVGA 01G-P3-1561-AR GeForce GTX 560 Ti FPB (Fermi) 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card
CORSAIR Enthusiast Series CMPSU-650TX 650W ATX12V / EPS12V SLI Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply
KB/M
Monitor
Logitech X-530 5.1 Speakers
2 3.5 HDD (1 500GB, 1 2TB SATA 3.0GB/s)

Preferred Website for Parts: Newegg

Country: USA

Parts Preference: I was thinking about getting an i5-2500, and 8GB of RAM

Overclocking: No

SLI: No

Monitor Resolution: 1680x1050

Additional Comments: When I build this machine would I need to do a clean install of Win7 or could I just plug it in and be good to go?

Thanks.

 

[nuke54]

Update:

I ordered the Intel Core i5-2500 Sandy Bridge 3.3GHz (3.7GHz Turbo Boost) LGA 1155 95W Quad-Core Desktop Processor Intel HD Graphics 2000 BX80623I52500

I was looking at the COOLER MASTER Storm Scout SGC-2000-KKN1-GP Black Steel / Plastic ATX Mid Tower Computer Case.

Now what I need help with is finding a good motherboard for it. And the kind of RAM to use. Should I use 1333 or could I use 1600?

Update 2: Could anyone tell me if this would be a good board to use?
GIGABYTE GA-Z68XP-UD3 LGA 1155 Intel Z68 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard