If you are looking to use this mahchine as a dj then I would assume you are wanting to get a Notebook so you can travel with it.
If so Apple themselves offer a lot of Refurbished units which come with full warranty etc.
You can get a Macbook with 13.3-inch glossy widescreen display1GB memory80GB hard driveCombo drive (DVD-ROM/CD-RW)Built-in iSight camera
For $799.00 from here http://store.apple.com/1-800-MY-APPLE/WebObjects/AppleStore.woa/wa/RSLID?mco=44BD9AA1&nclm=CertifiedMac
There are a lot of other options listed on the site also.
Let us know if you have more questions or need more info.