I don't think you can stream locally stored content to Amazon echo devices as Amazon has no way of cataloguing private content (apologies if I have misunderstood your intention)
I thought one could using say Plex
You can control a plex player (client) with an echo device but you can't use an echo device as a plex player (if that makes sense?)
I will probably rip using FLAC. So using your correct figure of 0.3TB a couple of 2TB in raid 1
give me quite a bit of play. If I ever did, and is a big ever, go down the video route can get bigger drives there and then.
I thought one could , with the caveat one can only use one alexa device at a time.
As far as I am aware you can use the Plex skill to control a Plex client (player) but you cannot use an echo device as a Plex client as they are not designed to do this, however if you had something like the SONOS one (which has some Alexa capabilities built in) you can then ask Alexa to play your Plex content on itself (the SONOS one) unless someone else knows different I don't believe you can have the same functionality on an Amazon echo device.
I did the same: The bitwise compression of FLAC doesn't achieve as high a compression ratio as things like mp3 which essential does a tran-code using "sum of waveform" Fourier type techniques, but FLAC means playback is as close to the original PCM on the disc as possible, so there's no question of loss of quality or dynamics (where I tend to "notice" any difference, esp. on "quieter" pieces.)
Incidentally, I used a program called Exact Audio Copy to do the ripping. It had some funky technology to optimise the performance of the drive one used and also had some kind of checksum process whereby it would compare my rip with a database of others (over the Internet) having ripped the same disc to give a kind of "confidence" score as to how well the disc had ripped. IIRC it tooka bit longer to do each disc (for some of the more ropy one, literally taking hours,) but if you are fussy about quality you might consider it worth the additional effort. It's also not the worst idea to give the platters a clean before you rip them. Some of mine were pretty mildewed!
"Some of mine were pretty mildewed!" Where do you do your listening, in the garden shed?data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
I am not greatly bothered about the rip quality, as being an old fart my ears are not what they used to be.
Of course - SWMBO doesn't appreciative the subtleties of my Motorhead and Slipknot collection, so I'm banished to the shed. I post a patrol of spiders and wood lice on the threshold to ensure I'm not disturbed. And she thinks the bottles I've got in there are full of (ahem) "weed killer."data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
Sounds you have a good setup there.