stuff is just probably dusty, you could get the CM Hyper 212 EVO heatsink and overclock.
Single thread performance really hasn't increased all that much to matter in recent years, I still see LOTS of people gaming perfectly fine on those old i7s and even to a lesser extent the older i5's
I want to tinker with an old i7 build myself, those i7 920s go for only about 60 bucks on ebay right now, the motherboards for 1366 x58 just cost alot in comparison. It would be cool to try out. I was wanting a secondary AMD rig, but eh, seeing how these old i7s stack up would be more fun maybe
It's certainlly not your CPU bottlenecking, it's probably just clogged with dust after these years.
You could get 4gbx3 ram sticks so you'd have triple channel ram as well as 12gb
maybe add an SSD for faster boot times and to make windows more snappy, but it's not required.
If you really have the itch to upgrade, there are 6 core Xeons (12 threads total with hyperthreading) that you can overclock I found by searching i7 920 on google and found a teksyndicate forum post where a guy has had his i7 920 for YEARS now and has an upgrade itch.
this Xeon costs about $115 on ebay, but like I said, your CPU is perfectly fine and just dusty.
search for this, "XEON X5650 6 CORE 2.66GHz 12MB 6.40GT/s 95W PROC"
https://teksyndicate.com/forum/cpu/i7-920-bloomfield-i-want-upgrade/162720