I have a 400 xi running a pair of gallo reference 3.05. While both units need break-in time out of the box, there has been no lack of bass response. I have driven these speakers witb tubes on the main input with and without the gallo sub amp on the 2nd voice coil. I also powered the main input with appropriate B&K and Bryston amplification. In the end nothing rivaled the 400xi except the tube/gallo setup that reqiured quite a bit of tweeking and a crazy feedback loop through voicecoil #2. In the end the control of the Krell in this budget minded application won hands down. Quite the pairing with a good/great DAC in line for the price. So my experience in regard to bass response via the 400xi, with budget in mind, the outcome is most dependant on the room, placement and displacement of the driver.