Listing your specs would be helpful, including your monitor's native resolution. There's only about a $10 price difference between the 7750 and 7770 when they go on sale. Unless you have to buy a new psu, then the 7770 is the better buy.
Is it possible to increase your budget slightly? A 7770 with Far Cry 3 was recently $78 AR: http://slickdeals.net/f/5957402-MSI...-Game-Coupon-78-After-25-Rebate-Free-shipping. Selling the game should make it slightly less than that. I'm not sure you'd do much better than that, even buying used, unless you increase your budget.
Obviously it's not on sale right now, but you could set up a deal alert for a 7770 and save up some more funds for it. A 7770 is over 20% faster than a 7750 in Skyrim. There's not much of a difference in Starcraft: http://www.anandtech.com/bench/Product/536?vs=535
If you're on a completely fixed budget, I have a 4870 512MB that I'd sell you for $50 shipped. You could probably resell it for $50 after you upgrade, so you'd only lose out on the shipping cost.
I'd keep an eye on psu prices and pick up the Corsair CX430 when it's $20 or less. I wouldn't trust that power supply. From your desired components, I'm guessing your budget is very low. The risk of that psu dying and taking all the components down with it is greater than the $20 cost of the CX430 IMO.
Why is a 720p 14" monitor your goal? 23" 1080p monitors are about $100 (http://www.pcm.com/p/product~dpno~9077086~pdp.hbfacbh), but that might be out of your price range.
At 720p, the 7770 should do fairly well. If you're going to upgrade the psu anyways (which I very much recommend), then the 7770 for about $80 is a good choice.
