Aiglon,
Your system might be a little weak for a DVD Burner, you will just not be able to do other things while you are burning on your comp. The prices on this end of the pond have been dropping quite fast lately. I picked up my Lite-On 4X DVD+/-RW Drive for $79. Make sure you get a dual spec DVD Burner. There are two competing specs right now, and you do not want to end up with the burner for the spec they drop.
The 8X drives are dropping in price right now, but the 4X seem to have stabilized. At this moment you can get 4X Media at a good price, but 8X media is very hard to find and it is at a premium. (Something to think about since the cost of all the media you will buy during the live of the drive will make the cost of the drive itself look like peanuts.)
Another option for you is a DVD/CD-RW Combo Drive. They burn CDs and play DVDs. They are within a few $$$ of a CD-RW drive and lets you read DVD Data Disks and watch movies.
Take Care,
Richard