I would not upgrade at this point in time.
It sounds like you have a decent system, but the step up will not be earth-shattering.
I would at least wait until Q1 when the Penryn is out as well as possibly NVIDIA's next Gen Chip.
Even if you don't want a 4-core chip, the Dual Core Penryn will be out Jan '20 and should destroy the E6850 with OC's reaching 4.5 to 5.0Ghz if I had to guess. I've seen those speeds on the Quads, though the 5.0Ghz took extreme cooling. The Dual would likely not require such methods.