I haven't heard either one, but the specs on paper suggest they aren't close (31 Hz vs. 39 Hz). The 20 XD has a more powerful amplifier but that's not enough to make up for the difference in cone area and cabinet volume. It's possible the 20 XD might have higher quality bass within its range though.
HT: Dynaudio C2, Contour S CX, 2x BM14S, Aperion surrounds, Simaudio Titan, Marantz AV8801, Oppo 103, Linn Majik DS, and a Pioneer Kuro
Stereo: Dynaudio Focus 160, Simaudio W-5 LE or Luxman M-600A, Linn Akurate DSM, 2x Rythmik F12G
Other interests: motorcycling, skiing, being active