Welp, based on some reading and some test results I've seen, it would appear that the conclusion is as follows:
Since I plan on getting the XP2100+ processor (266MHz FSB), the chipset to go with is the VIA KT400. If I were to go with the XP2700+ or newer (333MHz FSB), than the chipset to go with is the NVIDIA nForce2. It seems that the nForce2 chipset likes it best when the CPU FSB and the RAM FSB are the same. The VIA KT400 combined with a CPU with a FSB of 266MHz and DDR333 RAM outperformed the nForce2 combined with a CPU with a FSB of 266MHz and either DDR266 or DDR333 RAM. But, the nForce2 combined with a CPU with a FSB of 333MHz and DDR333 RAM outperformed the VIA KT400 with a CPU with a FSB of 333MHz and DDR333 RAM.
Looks like VIA KT400 for me.