[PLUG] How hot is a really hot? Dual Athlon MP on Linux

[Alex Daniloff]

Hello Lunux folkz,
Recently I've assembled Web, DB and file Linux server on Tyan Tiger
SMP2460 MB with two AMD Athlon 1500 MP CPUs.
The BIOS has a nice feature to measure CPU core temperatures in C.
Initially I used Thermaltake 6cu+ aluminum heatsinks with the copper
inserts. I used Dough Corning white silicone heat sink paste.
Idling CPU temperatures measured through the BIOS were at 35 and 36 C
on CPU0 and CPU1. It's good but heat sink fans sounded like a jet on
take off.
I changed these heatsinks on Millennium Glaciator I (not II) pure
copper heatsinks with built in fans.
They came with Cooling Flow heatsink compound. 
The server became very quiet but the idling CPU temperatures raised to
40 C on the both CPUs.
I can't take measurements directly from from CPUs only through the
BIOS and onboard sensors.
Could somebody tell me please if this temperature at 40 C is normal on
idling AMD Athlon 1500 MP CPUs, or it's a little bit to much?
Shold I change heat sink paste, fans or just live it like it is?

Thank you in advance for any thoughts or suggestions.
Alex