I would go for 200 x 12 the most important is the Bus, Why? Because with the bus your modifying the hole system speed, not only the processor one, a very fast processor is useless in a machine that can't go with it, so you must learn the rule "Low Multiplier, High FSB" but the best would be "High Multiplier, High FSB" but these is not a perfect world so choose a high FSB the temperature changes won't be high, at leat in the processor but keep in mind you're also forcing up every card in your computer, AGP, PCI or ISA, everything, and in some cases to force it too much may cuase data corruption, that perhaps you don't know but the CPU would have to ask more than one time to get the correct data, don't scare, just test the system after that with a good testing Software, like SAndra or better, the Microscope, good luck, and tell me your results
Mauro
PS: You have an AMD God will help you