i7 2600K with a 670? Even at standard clocks that should give you 60k+ PPD if you are 24/7. I assume you have hyperthreading enabled on the CPU which theoretically give you 8 CPU threads over the 4 cores.
The nvidia card does need a CPU slot with the 17 core GPU units, but if it drops back onto a 15 cored unit, that CPU slot isn't needed. However, set your CPU to 6 slots (SMP doesn't work well with odd slot numbers), as that gives it 3 full CPU cores. Both GPU and CPU use can fluctuate, on core 17s but you'd probably see your CPU running at about 90% of total (i.e. it's using more than one thread of one core).
It is a bit of a luck of the draw if you do get core 17 or core 15 GPU stuff, especially as folding are trying to use up the last of their core 15 units. You can increase your chances of the 17s by setting the GPU to the advanced flag. Technically you can use beta, but you should be a member of the beta testers group as those might throw up issues.
If for some reason you aren't completing WUs in their set timeframe, or they are regularly crashing, you don't get the Quick Return bonus, and thus your points will be low. WUs themselves are usually a lot lower in value than their total worth, due to the QRB. Focus on PPD rather than the WU values.