Safe NB temperature?

[SolitaryTurnip]

I'm trying to keep my pc as quiet as possible, and the second-loudest fan (stupid stock 6600gt fan is the loudest... I'll pick up a vf700-cu when I upgrade) is the NB cooling on my DFI nf4 ut-d. I can control when the fan should turn on, and I think I have it at 55c now and it rarely gets this hot, but I was wondering how cool the NB should be running. Should I leave it as it is or drop it down a little? Or is it even safe to leave the fan off until it gets hotter?

Right now, I'm all but idle, and it's at about 45c.

Thanks in advance.

 

[SpoogeMonkey]

I tend to not trust temp probes too much, so I don't have much faith in the mobo turning fans on/off for me. I would set it to turn on a bit earlier, if nothing else for oc stability and piece of mind.
If you can find a way to have a nice quiet 120mm fan blow on/across the chip, that would help alot.
This is the only flaw in an otherwise perfect board. They put the NB too damn close to the pcie slots