I agree with the post above.
I'll explain a little bit since you mention you don't know much about graphics cards.
Generally speaking a graphics card number will tell you a few things (though I'll only focus on Nvidia Graphics cards).
1. The first number, in your build, the 7 of 750 means it's 700 Series
2. The second determines if it's a low-end or high-end graphics card.
0-5 low end graphics cards.
6-9 High end.
So here's the catch. A 600 High-end series card is better than a low-end 700 series.
You can see it by Googling "GTX 750" click on the nvidia link geforce.com titled "GeForce GTX 750 Graphics Card | GeForce". Once there click on performance and scroll to the bottom. You can see the basic comparison of how each card stacks up next to each other. The GTX 660 scored 30,000 in the graph (3D Mark Vantage), and the GTX 750 got a score barely above 20,000.
Even a GTX 560 scores slightly better than the 750. And My old GTX 460 scores relatively close to the 750 with a score of about 17,000.
Then as for the case, you can definitely get something cheaper. It just depends on how much you want to cut back on looks.
Lastly, an optical drive isn't absolutely necessary, unless you already have windows on a disc. If you're willing to try some, you can try to install it via a USB. I personally have all my games on the cloud, so i don't have an optical drive.
