You could look into some of the unlocked Xeons, and a Throttlestop/Intel XTU overclock.
Multiplier-unlocked Xeons according to overclocking results from HWBOT: Bloomfield: W3570 (source) W3580 (uncertain) Gulftown: W3680 W3690 Gainestown: W5580 (most probably not unlocked, despite of one CPU-Z validation; please see also...
forums.servethehome.com
Since the unlock function is not official prices for these can be under the radar. Don't run the latest BIOS, or chipset drivers. Sometimes they lock them down again.
Her'es one with an i7-4790k
Here's an outstanding i7-4770. Not sure what this guy's doing but it sure looks like he found an overclock somewhere. 97% ranking for that CPU.
Here's one just to confirm what sort of Xeons run in those. This may not be an unlocked version.
So for the price of a Xeon and some free software you can see if there is any more potential in it before spending for cooling and RAM upgrades.
You can run yours there to see how much headroom there is for you.