For what I used, see: Image Viewer ASUS PUNDIT-AE3 AMD Socket 754 AMD Athlon /Sempron SiS 760GX 2x 184Pin SiS Real 256E Barebone - Retail $102.99. That's case, power, and mainboard for $102.99. Then I added an AMD Sempron 64 2600+ for $65, and a stick of 256 Mb RAM I had left over from another project, and an old disk that I had left over when I upgraded one of my bigger systems to bigger disks.
The company is horribly run with a slap it together and make it work attitude.
This is confirmend by my friends at Intel that have worked with ECS in Tiawan.
Prior to meeting (name redacted) I also owned a dual Pentium 166 ECS motherboard. Unstable junk.
For the small price difference you'd be crazy not to buy good quality hardware.
Like I said Asus and Abit (I've also heard good things about MSI but have no direct experiance). Let the Dell buyers get the ECS MBs. There is no point in building your own if you use the same junk parts all the OEMs do.