I would recommend the 1,3GHz Duron and a ECS K7S5A mainboard. The Duron is way faster than the Thunderbird, and the K7S5A will let you use the SD-RAM and also give you the option to upgrade to DDR later on.
Thank you all for your input. Based on information from here as well as other sources, I decided to to go for the Duron 1.2GHz, based on performance to price value. I also decided to dump the SDRAM for DDR.
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