GTAIV is a highly CPU limited game, you will not be able to play at high details unless you have a quad or VERY fast dual (4+ghz at least).
The GPU you picked is not by any means an enthusiast card, it will do well enough to play most games at medium details, but this depends a lot on the resolution of your monitor that you play at.
Its a decent budget system, but not a great gamer by any means. The PSU you picked is less than desirable, but at least you didn't pick an apevia or raidmax psu.
If you haven't bought this PC yet, you should post your budget and we will build you the best PC you can get for your money.