There are triple core options as well that can some times hit the sweet spot in your wallet .
I would probably stick with 2 x4 gig of RAM . Remember the graphics core shares system memory so the entire 4 gig is not available to the processor
A 300 watt psu is more appropriate . Total system draw is likely to be around 110 watts so save money here .
You have an OS . Make sure its 64 bit
RAID 0 has always been a hard mountain to climb . I doubt you will notice a speed boost from RAIDing two SSD's . How about a single SSD boot drive and a hard drive with much more capacity for data storage ?