Actually, live unamplified bass in the appropriately sized room or hall is delightful because of the many harmonic overtones which go up to HF. Take a French horn which has bass, although not as deep as a tuba. James Boyk has an essay called "Life above 20 kHz" or something like that. He showed that the French horn has significant energy up to 9 kHz. When you hear the French horn up close, it has tightness of bass, as well as midrange/HF. Bass by itself isn't tight, but the perceived tightness is from the much higher freq overtones integrated into the total sound of the instrument.
Bass instruments in various sized rooms have different tonal balances. The large piano in a small room sounds awful, because the walls reinforce the bass more than higher freq, creating a bass dominant heavy sound. The same piano on a large concert stage sounds lighter in tonal balance, with less perceived bass than in the small room.
The Goal Zero 400 is a special case where the high impedance is another factor to its detriment of bass. Perhaps larger inverters with lower output impedance is a big factor in explaining their superior sound. But impedance is only one factor. We can look up the impedance of the larger Yeti 3000, and compare to Giandel 2200 and 5000. There are probably other factors responsible for the superior sound of the Giandels, and whether the G 5000 is superior to the G 2200. Any of these units are a tiny fraction of the Stromtanks, so that's why I am going for the G 5000 which your friend vouches for.