The way I look at it, so far as collecting the quad reissues on Quadio or elsewhere, after one subtracts the classical (and shows/soundtracks) catalog from the quad discography list, there is really much less to collect. Then subtract the ones already reissued and you have yet even fewer titles. Take away the ones that the artists involved don't care to bother with and you are down to fewer yet. Then some lost or damaged masters, and the list shrinks even more. Bad commercial stiffs, yes some titles really are too obscure and lack any fan base and so are not in the running.
So after all these considerations I don't feel like there are hundreds and hundreds of quad masters to still reissue or that I really need to think long and hard before purchasing. There are simply not "that" many quad titles remaining from Sony, UMG, and WMG that imo are up for releasing. No need at all for me to worry about going broke buying these.
So I can buy all the Quadio series, enjoy each of them knowing there are not hundreds more yet to arrive or that I'd better be more selective.
There are dozens more things I expect to arrive, and not hundreds more. I'd like to hear them all. And if I don't end up liking some or I end up not wanting to listen to some of them, there is always that used market. I have never had a problem selling any surround disc in any format. Some of the titles I sold off went for pretty big bucks. I like to support the releases as they come out. And when they are out of print, I (sometimes) triple my original cash outlay with a sale.
Maria and Arlo are very low on my Quadio want list but I would probably buy them just to hear what they sound like in their fully glory as recordings & productions, ex and the quad mixes.