If space isn’t an issue, getting a cheap office surplus machine like a Dell Optiplex SFF line for ~$100 US vs the USFF so that it supports low profile PCI-E for a hba card for more storage, or nvidia quadro p400 for better encoding at like $30-50.
It will probably use a bit more wattage, especially with more HDDs, but still should be around 50w idle for even the old systems.