<< big difference, the the kt7a is based on via kt133a chipset. the kt7e is based on via kt133 enhanced chipset which is basically the kt133 with ata100 support
kt133=100mhz bus
kt133a=100 or 133mhz bus
basically to run any of the newer athlons you will want/need a 133mhz bus >>
Although the KT7E is known to run at 133MHz FSB without any problems. If your not looking for raid I don't see any reason you shouldn't get the KT7E.