cas123

Amd Phenom II x4 940
Gigabyte GA-MA770-UD3
Any name brand 2x2GB ram, cheapest price you find
Any name brand nVidia GTS 250, cheapest price you can find
2x Seagate Barracuda 12 st3320418as 320GB HD in raid-0
Antec/Corsair/CoolerMaster 550w PSU
any DVD-rw
any case

Should be around 5,000HKD, not including labor, OS and Monitor.
Cheapest good monitor photoshop/video editing I think is the Dell UltraSharp 2200WA, it has the e-IPS panel very accurate color.