Well, since nobody jumped in, I'll give it a try......
First, you
MUST accept that the terms "loud" and "acoustic bass" do not go together. You can try as many as you want but, the truth of the matter is that there is no such animal as a "loud acoustic bass". That is of course with the exception of an upright.
Armed with this cold, hard fact, here are some of my thoughts:
Some may try to tell you that the Tacoma Thunderchief is the only ABG capable of accompanying multiple acoustic guitars without amplification.
This is really only a half-truth. I have not owned a Tacoma but I've tried them out on various occasions. Truth is, if they
are louder, it's only by a very
small margin and it's not enough to not consider having to plug in.
I've owned several (more than a half dozen) over the past several years, both fretted and unfretted. Every single one needed to be plugged in when trying to accompany more than one acoustic. You might be able to get away with using a felt pick but, fingerpicking just won't cut it. Ultimately, the only way to reproduce that driving bass sound is to amplify. A small practice with no less than a 10" speaker should work fine.
Also, every fretted ABG I've owned seemed to have an annoying "boink" and, what I call fret rattle. Seems now matter how cleanly I tried to fret a note, there is almost always that "boinking" sound.
I kept searching, trying different rigs until I finally picked up a Michael Kelly Dragonfly Fretless Four.
Believe it or not, even the fretless had that annoying fret rattle with roundwound strings on it.
I bought a set of GHS Tapewounds, had a pro setup done and now, she sings sweet and low with no fret rattle and no "boinking" going on. Gets
very close to that deep, upright sound. I still need to plug in to get a nice, deep mellow "thump" but, it sounds awesome! I use mine with a little Crate BT50 bass amp with builtin octaver and distortion.
Many other bassists have enquired about and complimented me on the sound of my ABG when out on a gig.......even at some Bluegrass Jams that I've participated in. And
alot of those guys are purists.
I let a couple of upright players try my rig out and they've all absolutely LOVED it! So much so that there have been a few that have gone out and gotten their own ABG's.
Hope this helps! Others may have differing points of view but, this has been my experience with ABG's over the last 10 years. I'd also highly recommend a feed back buster sound hole cover since they're more susceptible to feedback than a solid body bass.
Forgot to include a picture, so, here it is on edit: