Operating System
Mac OS X 10.7
Mac OS X 10.8
Mac OS X 10.9 2
Mac OS X 10.6
Processor
i3, i5 or i7* 32 & 64 bit: 1.07GHz+ 3
* i5 or i7+ recommended when using Pitch ‘n Time DJ
Windows 7
Intel Processors
Core 2 Duo 32 bit: 2.0 GHz+ 64 bit: 2.4 GHz+
Screen Resolution 1280 x 720
RAM 32 bit: 2 GB
64 bit: 4 GB
4GB+ recommended when using Pitch ‘n Time DJ
USB Available USB 2.0 port
Those are the MINIMUM Requirement for your laptop to run Serato DJ
It’s a apple Ibook laptop 256 MB RAM 30 GB drive with a 12.1 inch screen
As you can see from the minimum specs, its 2 GB of RAM, while the apple laptop of your choice its only 256 MB, thats just askin for a lot of problems up ahead, stuttering graphical interface in Serato, latency in sound audio and among zillion other things,
I would suggest gettin a decent laptop by Dell, Acer, or Toshiba, laptop based windows is gettin cheaper and cheaper everyday, for 300 dollars you should get more powerful laptop than the Apple you suggested.
I understand you just doing this as a hobby, but if it finds irritates you more, you more than likely giving up on it