well, the i-3 its a such great processor for gaming! Even better than some Quad cores and indeed better than most AMD processors for $110-150 budget.. the bad thing in your built is the GTS450, i guess that GTX 550ti would be better for you.. in my opinion an ATI 6770-6790 would do a nice job, those are cheaper and BETTER than GTX550ti..
Also, at what resolution are you going to play? cuz if you only have a monitir which supports 1440-900 as max resolution, you really dont need a moster GPU.. just some mid range GPU as the 6770 i told you before..
The i3 is a much better processor, and actually is sufficient for your needs-- I have a system built with an i3 (and HD 6870) and I can play Crysis 2 on high with ease. In fact, I just was prior to reading this topic.
Look here: http://www.tomshardware.com/reviews/gaming-graphics-car...
If you want to put anything on high settings that was made in the last year, or something intensive from the past two years, you want to stick to generally the top six or seven positions in either ATI or nVidia. As an added note, go with ATi on a budget, as they really do give more value at any point below the $200 range.
Ideally, for what you want, I'd recommend a Core i3 2100 and a GTX 460/HD 6850 or better. You -could- go a bit cheaper with the graphics card, but you don't get nearly as good of value for your money.