I've always found that the problem with acoustic basses is that they basically don't work without amplification! No way you're going to keep up unamplified with somebody pounding away on a Taylor dreadnought!
If you really were serious about playing without an amp, then my favorite is actually relatively cheap if you can find one - look for a Kramer Ferrington bass from the 80's. They're generally not too pricey (these were made in Japan or Korea unless you find a real Ferrington which would be very expensive). Very loud and well balanced acoustically with a nice, electric bass-like neck. The piezo pickup is totally hopeless unless you have a reasonable external buffer amp though.
The Tacoma is good as well, although not as full sounding as the Ferrington. They're pretty reasonably priced too.
If you want to spend a LOT on one, then see if you can find one of the Taylor AB-1 basses with the huge body and offset soundhole. It doesn't sound as good unamplified as the Kramer, but again amazingly balanced, even if you get the 5-string one.
If you're going to be plugged in but want it to sound acoustic, the Turner Renaissance Amplicoustic basses are really good. Idiosyncratic neck profile (it's sort of strangely large). They have an excellent pickup, and you'll like the sound of the Thomastik nylon-core strings until you have to pay for a new set. This is more like an electric bass sound than an acoustic bass guitar (in fact, probably more like an upright bass than an acoustic bass guitar). This bass was designed by Rick Turner who was one of the early core folks at Alembic, so there's a bit of a connection there (although the relationship with the Alembic folks hasn't been good for a long time).
I've got a lot of basses that have piezos (Spector, Modulus, Parker, Bolin NS), but these basses all sound sort of like an unusual electric bass rather than anything like an acoustic instrument. I've also got a Veilette Mk IV 5-string fretless which sounds very similar to the Turner but plays more like an electric.
I tried many times to like the Martin acoustic bass, but it doesn't sound good at all unplugged and, to my ears, not that much better plugged in. It's beautifully built, but sort of a dreadnought with a long neck.
Go find one of those Ferringtons, you won't regret it!
David Fung