I've been meaning to post here and keep forgetting.
Case:
Looks great. I personally have a NZXT Phantom, love the thing, it's Darth Vader Black . The important thing is having space though and with a full tower you should be good, hopefully the interior isn't hard to work with(I haven't looked it up)
Processor:
The i5 vs i7 debate can change person to person. While I agree with Echo that most of the time you really don't need the i7, it can be handy. I currently have an i7 2600K in my machine, and the hyper threading makes a huge difference for me since I am a developer. I can reduce compile times of some projects by as much as 60% by opening it up to using all 8 cores (4 real 4 virtual, the computer can't tell the difference though). The actually speed (3.3 vs 3.4 GHz) isn't all that much, but the extra cache helps with larger programs as well (Think movie and photo editing software and, again, development environments). I believe the reason for the CryEngine running a little faster on the i5 is due to it not being optimized for the amount of threads the i7 provides. I'm not sure how much Star Citizen will improve that, but I'm sure as time goes on the CryEngine will be expandable to more threads.
SSD:
It depends on how much you care about the speed of SC launching is. You defintely want your OS on an SSD. On Windows 8 I go from pressing the on button to my desktop in 5.2 seconds, on a cold boot. I store my main applications on the SSD as well, but have moved my games to my larger 1 TB hard drive since games can take up so much space. You can easily store Star Citizen, your OS, and your core programs on a 250GB drive though ( Echo I'm not sure why your recommending another drive, I usually find it creates more clutter than anything else inside the computer, even with a large case, I reserve 3+ drive computers for servers mostly). Seagate is a good company, usually you want to base your purchase on the reviews which it seems like you have.
Graphics Card:
The 780 is an absolute beast of a card, I think your going to be good for a while. Something to remember though is Chris Roberts has stated that the top of the line graphics cards now will most likely run Star Citizen on medium settings. As for AMD vs NVidia, I've always been an NVidia guy. I know Mantle is coming out and is going to allow better access to the low level graphics hardware, but something to remember is that NVidia has the ability to make their cards Mantle capable as well. Mantle was designed as a platform agnostic API, so anyone can implement. Will NVidia do so? Who knows. If they start losing sales because developers are using Mantle and showing a lot of improvement over DirectX, then I would say they probably will to save face and continue making a profit. It's too early to tell.
Power Supply::
I've never used Roswell, thought I hear they're good. I have a Corsair TX 750W in mine. Again like Echo said make sure the voltages are all right, and that it will support the SLI that YOU may want in the future. It may be able to run two 660s, but not two 780s.
Memory
: I always say more is better with memory, which is usually true . I put 8GB into my rig (I built it in 2010) and it's served me just fine, but I do push the limits sometimes, and with SC, it wouldn't hurt to have more. The thing to remember with memory though is it's the easiest component to modify, popping memory sticks in and out is simple, so if you find you need more memory down the road, you can just add more, unlike a processor.
Optical Drive:
I barely use mine, it's nice to have every once and a while though. I picked up a nice Blu-Ray burner for somewhere around $80, which I'm sure have come down in price. If your going to put in an optical drive, I would say at least get one with a blu ray reader to stay with the times. I know some publishers are talking about releasing games on blu ray to cut down on the amount of disks you need. It's also nice to be able to watch blu ray movies on my computer .
Sound Card:
I've never actually seen the need for a sound card, but audiophiles seem to notice the difference. If you do get one Echo is right, make sure you get a decent sound system to complement it
Overall it seems like a great build. As I mentioned before , check out http://www.pcpartpicker.com . You can put in your components and it will check to make sure everything works for you, and also give you deals on where to buy stuff, or comparable parts for cheaps (Say an EVGAGraphics card instead of a MSI for $50 less). You can also add in SLI to see what any future requirements might be.
One other thing to consider is that over the next year a lot of things are changing in the PC industry. Next year will see the rise of DDR4 RAM, which will be faster than DDR3 by a decent amount and use less power. We should see an Intel processor update as well. As I mentioned with Graphics Cards, the longer you wait the better SC will look.
The problem with the PC industry is your always playing catch up. The turnaround on new tech is about 6 months, so by the time you've done your research and bought and built everything, something new is out. Usually I just say by the stuff when you want a new computer (usually trying to catch whatever the latest processor turnaround was), but it may be worth it to wait for DDR4 RAM and a few generations of graphics cards, depending on how antsy you are to play the alpha and beta
Hopefully this was helpful, good luck!