This Computer will come with 10.9 preinstalled. I haven't ran into any problems when running OSX on the computer. Everything will work out of the box when you receive the computer. Below are all the components that make up the computer + what I'm selling it with. I'm asking $590+shipping for the entire setup, And $520+shipping without the apple Bluetooth keyboard and trackpad. Basically I've gone through all the hassle of finding the most compatible parts so you don't have to. Feel free to ask any questions.
Antec Three Hundred Black Steel ATX Mid Tower Computer Case
Intel Core i5-3570K Ivy Bridge 3.4GHz (3.8GHz Turbo)
G.SKILL Ripjaws Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600
Cooler Master Hyper 212 Plus - CPU Cooler
Apple Bluetooth keyboard and Magic trackpad
SIX coolermaster fans
HDMI to VGA Adapter for dual screens