Well I'll share some of my thoughts. I have e6400. I reached 3.2ghz on stock air, but I was running way too hot. Past 61c. So I put it back down to 3.0ghz. Even then on full load (large FFTs, dual prime95) I hit 63.5c.
I picked up Zalman CNPS9500AT heatsink/fan. Which put the temps to 43.5c full load. Now I am at 3.4Ghz and my temps don't go past 53c full load.
I had to set 1.5v in bios to to be stable at 3.4ghz. Although according to Pc Probe I am only using 1.395v.
I had prime95 running dual core fine for about 20 mins at 3.5ghz. But my temps hit 60c and well I don't want to run it that hot.
I know intel says 61c max. But thats at stock speeds and stock voltages. Being overclocked I don't want to go past 55c.
Originally I got a P5N-sli. And that board was crap! The northbridge heat sink was sooo hot at stock speeds I could barely touch it. And an overclock to 2.3ghz resulted in boot failure.
This P5B has been working great so far for me. (The one the guide says to not use)
That guide does not go into what the max temps should be for your cpu.
I don't know about the other ones, but for E6400 I would not go past 55c overclocked. People have gone past 61c and continue to run at those temps. But after a lot of researching, I have come to peace and mind at 55c.
I think the reason for not recommending the P5B is because with the old bios, your FSB is limited to 400mhz. FSB Termination is limited to 1.3v and ram is limited to 2.1v.
Well with the latest bios. FSB is limited to 650mhz and FSB Termination goes up to 1.45v. But the ram is still at 2.1v. But hey I am running just fine at 2.1