B-80 is right. If you want the chip to work 5-10 years down the road, don't abuse it. If you don't care and will upgrade in 2-3 years, f*ck it and o/c and enjoy it. FYI - Intel's specs
on the E6600 have a max core temp of 60 °C if I'm reading it correctly.
But that didn't answer your question: I'd say you do the most CPU intensive thing you will ever do on the machine and log the temps as you go. Do you plan on running orthos everyday? I doubt it. Orthos is good for helping you identify the lowest voltage you can run @ since it reports errors if the CPU becomes unstable. If you're concerned about your temps, my advice is:
1) Get a good better HS. Your P180b will fit an Ultra-120 Extreme which uses a 120mm fan and is likely the most efficient
HS on the market today.
2) Lap the HS and IHS on your E6600. Doing this dropped 7-10 °C off my load temps on my q6600 (7 on the coolest core and 10 on the hottest core). It'll cost you under $20 to do and will be the biggest bang-for-your-buck cooling period.
3) Make sure your have good case air flow.
4) Find the minimum vcore you can use for your overclock. In other words, find an o/c you're happy with (9x333 is good enough for me) and then drop the BIOS vcore, boot into win and run several orthos. If it's stable for 5-6 hours, drop it again and repeat. I'd say you'll wanna start at a low value and work your way up since if it's too low odds are you'll crash right away or soon. Took me several times to find that my q6600 running @ 9x333 can do so @ 1.3125v. Lower voltage = less heat output.
- Great core temp measuring util with great logging options.
My Q6600 lapping result (pics and temp data)
My Ultra-120 Ex lapping result (pics and temp data)