Its safe. Im on a rock solid 175mhz on my 2400. Some even go to 200 and more.
Athlons like the xp2500+ run at 166 standard.
Total mhz relates to watts used. Watts produce heat. If your internal clock stays the same your temp will too.
You might need some extra cooling on your chipset chip. Get another fan or two.....there goes your quit pc, but it will be faster
