Thank you for your reply. Yes it is core i3 2100.
I probably will upgrade the PSU. There is not much of a difference in the prices of GTX 650 Ti and HD 6850, is the later any good than the GTX 650 Ti?
And is processor going to bottleneck the GPU?
Upgrade it. Here is the problem even low power GPUs are going to push your system and likely shorten the life of the PSU you have currently. An upgrade for a 550w or so is dirt cheap and will expand what you can get.