I purchased a prodesk i5 6500 with a 500gb ssd, 8gb memory and windows 10 pro from ebay for 200.... Migrated from a nuc 4250 for 8 cams... Works great.
Thanks to the OP and the quick and dirty poster of the instructions. Worked perfectly to go from 5.2.5 to 5.4.5. My camera was mysteriously reset so hopefully the upgrade does the trick.