Yes, your system will be a bottle-neck. Not a huge one and it would benefit greatly from a 7850, but it would be a moderate bottle-neck. You would need a faster CPU and faster memory to get the full benefits of the 7850, but even with your current system, it would be near the full speed of the 7850 in most games, so don't worry about it. Buy the 7850 if you want to and when you upgrade the rest of your computer, just move the 7850 over.
What if I overclock my processor? I have hyper tx3 cpu cooler. will it bottleneck at 3.6 ghz? I will play on 1920x1080 resolution so I think at that resolution,gpu will be more important than cpu.right?