RAID 0 will give you about twice the performance of a single drive, but only in drive-intensive tasks (such as level loading in games). It won't make any difference to your framerate when gaming, and probably won't be noticeable when just web-surfing. It also gives roughly twice the chance of failure (because if one of the drives goes down, the array becomes unusable; it's not exactly double the probability, but close enough), and will actually slow down bootup, because it has to check the status of the drives and give you time to press a key to adjust the RAID configuration.
At that budget, I'd suggest this for the ssd:
http://pcpartpicker.com/part/samsung-internal-hard-drive-mz7pd256bw
and this for the hdd:
http://pcpartpicker.com/part/seagate-internal-hard-drive-st4000vn000