So I have this computer with:
HD radeon 5450 512mb
intel i5 650 3.20ghz
And I can only run it with 30+ fps on 800x600 with lowest settings possible.
What is holding my computer back?
If its graphics card only - is a gtx 560 ti a good choice to run games like mw3 black ops and battlefield at 1440x900 at high settings?
Yes its the graphics card .
At your resolution you wont need to spend as much as the cost of a 560 ti
A Radeon 6870 or GTX 560 will be as much graphic power as you will need and then some .
You also need to check you have a 500 watt psu and you have the required power connectors for the graphics card .