It is uncommon to hear that 3.6 is bass shy. At the same time, I do not doubt Classe, however, will not rule it out entirely.
This is what I would do if I encounter the same situation - first, check the physical conditions of every driver, woofers, and the surrounding rubber. Look out for some clues of deterioration or cracks. Next, monitor and observe the behaviour of the woofers, especially with a bassy music track. Look out for driver excursions. It should look tight and fast, with minimal or zero "lag". If all is looking just fine as "how it should be", next pair the 3.6 with another power amplifier, and again continue to monitor and observe the behaviour of the woofers.