New GPU?

You will definitely see an improvement by upgrading your CPU. Most games aren't that CPU intensive, so you'll only see a small improvement in fps. However if you are doing something like streaming yourself playing games, then it might start to feel chunky.

What I'm worried about is if 550W psu will be enough. Not sure how well the power consumption of the 7990 is going to be, but it's always good to stay under 80% psu load, so 550W might be pushing it a bit. It may be good to upgrade to a 750W psu. I'm no expert in PSUs, so someone else should confirm with me.

550W will definitely NOT cut it for any Dual-GPU solution. What exactly are you trying to play/do? Also, what is your resolution?

the "upgrade" to the cpu........... I have a 1090T and it get's stomped by a Q9550/775. I wouldn't waste money on another cpu.

the gpu........ depending on your opsys and monitor/res/games-apps........ that will dictate your needs.

the PS......... got 50amps or more ? if not I wouldn't use it for the new card.

I know I'll have to upgrade my PSU  . I'm just playing the newest games. I'm playing on a 40" sony tv with 1080p.