The GTS 250 is the same thing as my 9800GTX+ it is just rebadged and it is getting a little weak at anything over 1440x900 resolution. It is NOT really well balanced. An HD 5770 would be a better choice or best would be a HD 5850 if you can afford it. I can not really recommend Nvidia as Ati has more " bang for your buck" at least right now.
Also an SSD will do nothing as far as making games play any better. It will only decrease load times.
The i5 750 with 4GB of RAM is fine though.