i'd go with a single 256 stick to leave room for future upgrades
the ecs k7s5a is a good duron board, fast, really cheap, onboard nic, workable onboard sound, not big on overclocking options but it doesn't sound like that will be a problem for this setup
make sure to use good quality ram and a good amd certified psu
the board has an option to run at 100 fsb/133 mem so pc 2100 memory will work great despite the durons 100 mhz fsb
looked up that nforce board....nice board...but twice as much as the ecs board
unfortunatley the dual channel ddr of the nforce didn't really work out as well as one would have hoped...my kt333 based board gives it a solid beating in bandwidth
the only real advantage to getting the nforce board would be if you have speakers good enough to take full advantage of the onboard sound (i.e. dolby digital 5.1 system)
so giving that caveat..i'll reccomend the ecs board