68C is cutting it close...may result in degeneration over a long period of time. Maybe get a new heatsink...you should try to keep it below 65C...under 60C would be even better.
Intel's thermal spec is 72.4c, but since they have not revealed the true TjMax value, there is no way to know for sure what the real core temps are. The TjMax value is believed to be in the region of 95c to 105c (45nms confirmed as 100c by Intel). That put you within a margin of error of 10c.
I would be happy to set a rough limit of around 70c using a TJMax of 100c. Both CoreTemp and Realtemp use 100c in their latest releases.
isnt quad cores hotter since theres 4 cores as opposed to dual which has 2 cores?
Can you please run the sensor test in Real Temp, preferably v 2.75 or later but 2.70 will suffice for the sensor test.
Which cooler are you using?
Your load temps sound a little elevated, you don't say what the cpu was loaded with (IntelBurnTest will give you max temps when run on max stress)
If it is indeed the stock Intel cooler I suggest you check (and I mean physically check) that all the push pin mounts are still engaged, they are a terrible system and let go / disengage sometimes.