That sounds like something made to run Crysis at max on a 30" screen rather than a stitching and PS computer, as the components are massive overkill for a stills shooter, I don't care how big your stitches are. You could go down a price range or two on every component you list, and still get 90+% of the performance for ~half the price.
I'm not familiar with those GPUs, but have you actually compared 8-bit output to 10-bit? No, looking at a computer/monitor combo at a store doesn't count in most cases, since they make the cheap ones look crappy on purpose. If 8-bit is ok, you could slap an X1950 on it and you couldn't tell the difference in PS. Crysis, certainly.
I'd ask myself whether that 750 USD you could save would make you a better photographer by spending it on a new lens or a workshop, or a bleeding edge computer with a huge premium. But it's your money so go for it if that's what you want...
I second comments on getting a proper UPS and case. Blowing 1500 USD on a computer and having the PSU, mobo, CPU and/or GPU die because of a spike is not nice. Many so-called surge protectors are snake oil and don't do what their name claims. Oh, and you don't have to splurge on a UPS which actually gives you 10+ minutes of power - who on earth takes 10 mins to take down their computer? Good case will allow for better airflow (read: longer component life), and make those Spinpoints and that ridiculous GPU quieter.
Also, you can save quite a bit of money by ditching that one OS SSD. Win7's SuperFetch essentially nullifies SSD performance boost over HDDs as OS disks.
Don't listen to the kilowatt PSU guys, you don't need it. There are good PSU calculators online, use one and add 20% to be safe. High efficiency is good.
I'm never going to buy another WD drive after my raptor died, and it took over a month and numerous emails to get their damn RMA to work (this was via their German branch). These guys
who build 135TB (yes, one hundred and thirty five terabytes) storage arrays on the cheap also say WDs (and Seagates) have much higher rates of failure, and swear by Hitachi. I've used Samsungs for years and am very happy with them and the bang-for-euro.
You haven't mentioned how you do or plan to do backups. FWIW I have a daily backup to a HDD which is in my case, a weekly to an offline USB HDD, a monthly to a HDD which I keep offsite (fire, theft, etc.), and CrashPlan for redundancy. And RAID is not backup.
a. 64gb SSD's for most people come up short on capacity. SSD's lose performance at the 70-75% fill rate vs. the 50% for hard drives.
What do you mean by "performance"? I just ran ATTO benchmark on my Vertex I bought over a year ago, and its read and write speeds are unchanged since it was new. It's 87% full and always has been, and I don't even do garbage collection, idling, or any other kind of maintenance. Is this the same FUD as those claims about short SSD lifespans?