[metildaa]

I like the OrangePi lineup, particularly the OrangePi PC Plus as it has 8GB eMMC and decent specs while being sub-$30 with a case and accessories: https://m.aliexpress.com/item/32668421022.html

For a NAS, nearly all of the OrangePis feature USB ports & ethernet that are directly wired to the SOC, so you aren't I/O limited like older Raspberry Pi's. That being said, the Allwinner H3 doesn't support 10 bit Hevc/H.265 acceleration, so you might want to go with a board based on a newer chip for a HTPC. Take a peek at LibreELEC, they have a decent HTPC distro for many SBCs.