You'll need a fourth 150Gb Velicoraptor to construct a true RAID 0 + 1.
If money's no object go for 4 SSD hard drives although putting them in a RAID config won't necessarily gain you any extra speed, they read very fast as single drives.
4 x 256Gb SSD's will currently cost you around £850.00 from Crucial, amongst others.
If you're not gaming and money's no object consider a Quadro card, ideal for CAD work
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Prices
Two or more graphics cards will not gain you any significant performance increase other than in games and even then it's negligible.
All the rest looks good. You may want to consider a Noctua CPU cooler, they're very good. Having said that, the Intel i7 stock cooler is very good indeed, best stock cooler I've ever seen.
You may also find this thread of interest.