11-25-12: PdreherPaul, you've provided some excellent comments IMO. However, I would point out that the impedance curve of the M40.1 is anything but flat. While its impedance characteristics represent an easy load, apart from its somewhat low sensitivity, and I have no doubt that the XA60.5 can drive it with ease (especially in a 13 x 16 room), the deviation from flatness will result in significantly different tonal characteristics with a solid state amp such as that, in comparison with a tube amp. For example, a solid state amp, having negligibly small output impedance, will give greater emphasis to frequencies around 500 Hz, where the impedance dips to low values, while a tube amp, having significant output impedance, will give greater emphasis to frequencies around the speaker's impedance peaks occurring near 1.2 and 5 kHz.
The Harbeth M-40.1's have a very flat impedance curve and are 6 ohm nominal... so your PASS amps would be more than powerful enough for them. I've driven them with tube amps ranging from 3o watts to 75 watts and they sounded great with all of them.
Having no experience with the speaker, I can't comment on which kind of response is most likely to be preferable, although obviously you and many others have been very pleased pairing it with tubes.
TheGoodArcher, my only other comment on your candidates is that I would eliminate the Maggie 1.7 from consideration, as I don't think it would provide the bass response your other recent threads have suggested you are looking for.
Regards,
-- Al