I heard the 2Pi and 2Pi Towers years ago. 2Pi don't do much real bass, 2Pi Towers do a bit better. Like most high efficiency designs, deep bass (under 40 Hz) is missing.
As you know, those nasty laws of phsyics say pick one: bass, size, or efficiency. The most clear exemption that I know of are Hawthorne Silver Iris ($320/pair of coaxial drivers, easy to build, small baffle. The 15 inchers will reach 40 Hz in-room at 96 dB/w/m. The 10 inchers integrate the woofer/tweeter better but gives up some of the bass. Not the most resolving (unless you want to spend more).
If you were open to active designs, you can relatively easily get big bass in a small package. Event 20/20 BAS (Big Ass Bass) is one example ($900/pair USD, 35 - 20,000 Hz, 14x10x11).