Hello dude.
If you are upgrading the 920 you will also need to change your motherboard and possibly your ram as you will most likely be moving to another socket such as 1155 or 2011. If you are intending to stay with the current socket (1366) and upgrading the cpu then I would personally not do it as it would be a waste and overclocking the current CPU would be a more viable option with an aftermarket cooler (if that is an option you feel comfortable with and have a chip that is willing).
I have been looking into a 7 series GPU as an upgrade myself and am trying to find out some information regarding processor bottlenecks between 920/930/950 processors as I am running a 930 @ 4.2 and am still very happy with it but I haven't found it to be a limiting factor with my current setup. Will try and find some info and link to it.
Let me know if that 500 bucks is for processor, motherboard and RAM and will have a peek at best option.
Edit: Took so long rambling that got beat to it