Can i play GTA IV with this specs?

bottleneck? no way will a gts 450 bottleneck an i5...
it doesnt have the bandwidth for 1...
i run the pc in my sig and its not as strong as the 2500k but my gfx would eat that 450 and still have room for more...

i play gta 4 on the max settings apart from drawdistance because the game needs 1.5 gigs to max that out and my gfx is only 1 gig...
so no there would be no bottlenecking of the cpu with that gfx... and the plank in the shop who told you it would should go work in the stock room instead of behind the counter.
smitty im suprised at you for that 1... the only way that gpu may bottleneck is because your running it on such a small screen but even then i cant see it because it should free up some vram to increase draw distance...

in reality that cpu is overpowerd compared to your gfx and it will handle any gpu you throw at it. yes gta is cpu bound but the 2500k is a monster compared to the old core 2 quads and they handled gta 4 with ease...

when you have the cash get a 560 or even a 670 and your cpu will be very happy to run it... but you are gonna have to update that screen with something bigger if you want to see the true performance of any decent 1gig+ gfx card.