Are you talking about those short little 1u passive heat sinks? I wouldn't consider using them unless you had a proper corresponding chassis, cooling fans, and airduct that would tightly mate with those heat sinks to force *all* the air through them.
The BMC webconsole's sensors page will provide temps (not CPU temps directly), however you can derive the CPU temp from the P# Therm Margin values. Note, if they drop below ~20%, that indicates that your CPU cores are very close to 80c. The stock Intel cooling setup for that board will ramp up the cooling fans so that a system will stay above the 20% P# Therm Margin.
I'm looking at my temps to make sure everything's in line, and I'm seeing P# Therm Margin being reported in negative Celsius, while P# Therm Ctrl % is 0%. Do you know what 0 degrees C is supposed to be in real terms for thermal margin? When I run stress tests, I can hear the fans ramp up, and System Board 1 Agg Therm Mgn 2 goes from negative to around +6 C and trips the alarm. All other temp margins remain normal/negative. I'm in a P4000M case with dual 750W power supplies. Is this expected behavior?
Also, when I ran the BIOS/ME/FRUSDR updates, I forgot to connect to I2C cable from the backplane to the motherboard so it wasn't detected. Do you recommend connecting the cable and rerunning the FRUSDR updater? The drive activity lights appear to be working even with it disconnected.