Buying a used computer?

I recently came across this ad for a used gaming computer. The specs and add-ons read as follows:

- Rare Soprano case (with door hinges on the side for easy internal access, and a curvy front end which opens up to reveal DVD/CD Bays and power switch)
- Intel Core 2 Duo 2.8 Ghz Processor
- 6 GB RAM
- Runs Windows Vista Ultimate
- NEW ATI Radeon 4870 HD Video Card (literally a month old)
- NEW Western Digital Extreme 1 TB Hard Drive (For all games and music. This is the main storage hard drive)
- Western Digital 80 GB Hard Drive (For anything having to do with the operating system)
- DVD-ROM Drive
- Extra CD-ROM Drive
- Sound Blaster sound card
- PCI Wireless LAN 802.11 Card w/ 3 Antennas
- HDMI Capable (with correct tv or monitor supporting HDMI)
- 8 USB Ports
- NEW ThermalTAke Heatsink
- 3 Blue LED Fans inside (2 attached to the inside of the case and one on the heatsink, all of which keep the computer cool)
- HD Audio Input (in case you buy a sound system like that)
- Comes with all cords (including HDMI cable) and adapters for your monitor.
- Comes with Logitech WAVE Wireless Keyboard and Mouse ($70 Dollar value)
- Comes with Logitech Gaming Headset ($50 Dollar Value)

The cost: 600 obo

My questions are:
-should I buy a used computer?
-is this computer a good deal?

I don't have much money about $600 to make a computer and I have a core2duo extreme edition proc but don't know how much it would cost to go that route. If anything, should I wait for an i7 setup?

What's the best route for a gamer and light video editor?