Raid doesn't solve anything... A defect bit on a drive will happily be copied to the other drive yielding two corrupt files.
It feels as if you are wasting money on stuff that brings nothing to the computing experience.
Get an intel SSD of 120 gig. Install OS and apps ther. Get a WD black and use that to storeyour home directory and data. Run windows 7 backup tool to make a golden system image once al software is installed. If the SSD goes belly up : reload from the sysimage. The sysimages are about 5 to 10 gig depending on how much stuff you got. If you copy all data then they are larger ). Make a duplicate of the sysimage on an external usb drive. Laptop style drive. Those are cheap. Worst comes to worst you can redeploy from there that drive lies on a cupboard, disconnected and powered off until you either need it to recover, or want to update the sysimage.
Now, i am talking purely technical apps here, i don't game, so you'll have to tweak my advice toward you liking.
Intel i5-760. Older cpu , cheap but a true quad core. Stock cooler is dead quit
Intel dp55bw or gw mobo. Bulletproof, nu futzing with overclocking. Built like a tank. I got about 20 of those in the lab ( we build or own ) and 4 at home.
True 1.5 volt memory from a reputable brand like samsung, kingston or corsair.
I use a simple nvidia graphics card with two dvi ports and 1 gig memory. I think its a 500 series. Was like 75$...
4 gigs of ram ( we still run 32 bit win7 )
That thing churns through Altium , solidworks , visual studio , Altera and Xilinx software , matlab , cadence viewers and all kind of other hi- end software without blinking.
And you can get that stuff dead cheap because this is an older generation cpu.
I stick em in Antec titan cases . Because they are long and squat. They dont topple over if you bump in to them and have lots of room. Since these are lab machines the sides are off. The antec psu in the titan is 650 watts. Plenty for what we do.
We typically have additional sata boards in there with multiple drives on it, sometimes 12 per machine ( advantage of the titan case. Lots of room for drives.... But then again, we develop drives so thats why.. )