For a HTPC I think 60GB64GB is the sweet spot. Anything smaller and at some point you’ll either have to sacrifice caching (page file, %ProgramData%, etc.) or do regular maintenance,
For a primary workstation I need 128GB or higher though. Development kits and IDEs are huge. With the bare minimal I need for work it is close to 52GB full and with a 60GB that just doesn’t give enough head room for Service Packs.