I have about 33k tracks and MinimServer uses ~200MB of RAM, but that's with a lot of tags indexed.
During scanning memory increases to 500MB so that's the likely point of failure, although if only a handful of tags are indexed 8GB might be enough.
I couldn't imagine giving up control of the scanning process to a black box like the Amp/WiiM.
Picoreplay doesn't use much either nor in HD space, but the database index can once it catches album art. My pi has 4gb of ram
Database is on 64gb 2.5" ssd
Wiim is quad core so fast enough, but lack of ram could be issue during scan on large database.