2-way speaker with best bass

Shadorne you didn't mention the transmission line cabinet. Helps to get optimum bass from a small woofer. My Meadowlark Shearwater Hot Rods--a TL design--have great bass for a two-way.

If you want to get bass below 60Hz from a two-way, you can get it. You have to choose your speaker carefully -- the Merlin VSM mentioned above and the orphaned Meadowlark Shearwater are examples -- then place it well. Realistic, tuneful, articulate bass, yes sir, and low enough that the wavelength is too long for the room and them low lows wind up in the kitchen. Punch you in the spleen and flutter your shoelaces, no.

Not forgetting to give your speaker good electronics, a good source, good cables... all things that affect bass from any speaker, just like placement. I would mention room treatment but a poor room also will keep a more-than-2-way from giving decent low end output. But the OP knows about all these, and the crossover tradeoff factor, and bla bla bla.

So to answer his question : Merlin VSM and Meadowlark Shearwater Hot Rod IMO, and I'm sure there are others.

It is impressive, at least to me--the Shearwater's bass, that is. For a two-way, it's exceptional. Mr. Atkinson is more rolled-off in his praise:

reasonable bass extension

--this from the link you kindly provided, Shadorne.

I can see the dishing in the upper mids from 1K to 5K in Mr. Atkinson's tweeter-axis plot, but like other points he brought up in his test series, it didn't seem to bother the reviewer (Chip Stern). I can't say it bothers me either, perhaps because my as-yet-untreated room is quite lively.

If you'd like to hear for yourself how Pat McGinty managed his tradeoff in the Shearwater design, you're welcome. Drop me a line if you come to Montreal.