If you can find an additional 8GB of DDR3 on the cheap, you should be able to squeeze a bit more life out of that i7. It's not going to be amazing, but it's not going to be terrible either. But I would seriously look into upgrading that PSU. You'll still be able to use it in future builds so it's not a bad investment now.
Looks like your non even 80+ rated PSU made it on our Tier E list. Tier E meaning "Potentially dangerous in multiple scenarios".