Need help building computer

[ii lucky charm i]

Hey guys, I'm building a new computer and I need your helps!

I need something that can do the following smoothly (meaning without any freezes or lags):

1. Browsing the Internet
2. Photo Editing (Photoshop CS4 and GIMP)
3. Microsoft Office / Excel / Powerpopint
4. I usually have 3 windows open at any one time. I don't multitask that much.

I also need a 19-inch screen.

The maximum amount that I can spend is $600.

 

[Benny Boy]

Can you buy from here?

This leaves about $50 for a case.

Acer V193WEJb Black 19" 5ms Widescreen LCD Monitor
　
GIGABYTE GA-880GA-UD3H AM3 AMD 880G SATA 6Gb/s USB 3.0 HDMI ATX AMD Motherboard
IGP will do CS4 / GIMP / Microsoft Office / Excel / Powerpopint
/ 2 monitors / 1080p
AMD Athlon II X4 640 Propus 3.0GHz Socket AM3 95W Quad-Core Desktop Processor ADX640WFGMBOX

G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Dual Channel Kit Desktop Memory Model F3-12800CL9D-4GBNQ
Promo with eblast sign up DM15A02US

Antec earthwatts EA500 500W Continuous Power ATX12V v2.2 80 PLUS Certified Active PFC "Compatible with Core i7/Core i5" ...

Seagate Barracuda 7200.12 ST3500418AS 500GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive

500w is a little much but it allows for upgrade to dedicated video card if you go that route.
The x4 fits the budget, but for the duties you describe an x3 will do just as well for less.
AMD Athlon II X3 450 Rana 3.2GHz Socket AM3 95W Triple-Core Desktop Processor ADX450WFGMBOX