What you need is a disks with a P-Ata interface (falsely called IDE). Whether Udma/100 or Udma/133 isn't important.
Check the Web for any known incompatibilities (bugs) between disks and VIA KM400A.
P-Ata is more expensive that S-Ata because the interface costs more to produce: chips, connectors... And because competition has shrunk now. But they're affordable at eBay - as opposed to mainstream retailers who scrapped P-Ata from their offerings.
I bought many used disks and had no more trouble with them than with new disks.
The latest fast disks in P-Ata is the 7k160 (= J8160), but is limited to 160GB. Others have somewhat slower arms.
- Add a S-Ata host on a Pci slot. Bootable (check it before), no size limit, modern disks. BUT the Pci is limited to about 70MB/s at Via so you'll have to look for unofficial software fixes for the Pci.
- Throw away your Via, as its hardware is full of bugs.