I use foobar2000 for all my database management, its a learning curve but very powerful with all the plugins and scripts available.
mp3tag is also useful for somethings like seeing multiple embedded album art.
i download everything to the nas in its original format in its own dir
like amazon, itunes, beatport etc in either singles or albums
then i duplicate that into the main music file structure after tagging as i like in foobar2000 with a script as follows
music/genre/artist/album/01.title.mp3
or for an album with various artists
music/genre/various artists/album/01.title (artist).mp3
for singles in a flat format like this
music/singles/artist-title.mp3
for singles i embed album art so it shows in the car and on my mp3 player and media center properly
for albums i just add the cover as folder.jpg to the album folder
i use rsnapshot/rsync running from the nas to automatically backup everything to another drive
to copy tunes to another device i just do it from explorer or foobar2000 to copy what i like.
checkout subsonic/madsonic to stream music from your server to your pc and android devices or use a server like serviio so you can access all your tunes via dlna on your devices
i dont currently have this lot in a cloud as basically i have a lot of music and no one service currently provides what i want.
all sounds like a lot of hassle but really isnt now its all setup as i like
if you use multiple services for music then it can be a pain to keep all consolidated and working smoothly.