Help Choosing Components for Mid Range PC

Time frame: I plan to purchase in the next 7 days.

Budget: As inexpensive as possible! But I'm prepared to spend $600-$850.

Usage (in order of importance):
1. Playing online poker.
2. Running a postgres sql database (~40GB).
3. General web and email.
4. File storage (~100GB).
5. Very light video encoding.

Parts not required:
Keyboard, Mouse, Monitor, Speakers

Preferred website to purchase:
None, although I would prefer to purchase from one place.

Parts preferences:
1. Multi core AMD processor. I need multi cores, but Intel is not worth the $$$ to me. I prefer quad core, but would consider three or two core processors.
2. Two hard disks in a RAID 0 configuration (for better read/write performance to my database).
3. Video card must support two monitors with digital output. However, the graphics are low intensity and not fast moving, so high end cards and SLI/Crossfire type technologies are not important to me (at least I don't think so).

Overclocking: Maybe

SLI/Crossfire: Doubtful

Monitor Resolution: Currently 1920x1080, although I may upgrade to 1920x1200.

Will plan to run Windows 7 OS.