http://pcpartpicker.com/p/7wdVbv
This is my new gaming rig system build after 3 years with my old one running a GTX 480(too hot). This build include a monitor and OS. Also, is the SSD enough for Windows only. If you have any suggestions around this price range, please leave a comment. Keep in mind the prixe includes mail in rebate.
If you plan to OC You will need better than a stock CPU cooler if on a budget th CoolerMaster Hyper 212 evo is about $29 and is a good cooler for mild to mid OCs
You may also need at least a 550w 80+ bronze PSU for more stable OCs on System and GPU
Looks solid, the r9 270x and r9 280 perform about the same in the tests i've seen. You could get the r9 270x and use the money saved for a CPU cooler.
I could also jump to a 285, it's only a $10 difference with mail in rebate.
This is What i'd do. I have a personal preference of Nvidia but thats just me.
I also put that card in there as a reference this 660 is on newegg for $135 which outperforms the 750ti a little.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814500270
http://pcpartpicker.com/p/t6MWyc
The 660 is a silly choice.
You can get an R9 270 for $100-$130. It destroys the 750 Ti.