I have no personal experience with the Hansen Prince speaker but reading the specs 87dB and 6ohm nominal seems like borderline case with the Shindo. I pulled up the Stereophile review and in John Atkinson's measurements section, he measured the Prince's sensitivity at 85dB a little lower than Hansen's stated rating of 87dB, however, importantly the speaker does not got below 8ohms between 10-200Hz in the bass region so it will not present a difficult load in the bass region. It does dip below 4ohms in the mid-treble region and up (from about 2.5KHz and up)never going below 3 ohms it looks like. This suggests that with a tube amp, the high frequencies will be a bit of a tougher load on a partnering tube amp and may be somewhat attenuated. Here is the relevant section from John Atkinson's measurement section:
Here is the impedance and phase angle graph across the frequency spectrum: http://www.stereophile.com/images/archivesart/408Hanfig1.jpg
My suggestion, take your Shindo Sinhonia amp with you to the local dealer who carries the Prince speakers (if you have someone locally) and try them out. You may get a sonic signature that you like but purely from the impedance graph it sounds like you may have attenuated high frequencies/treble and heightened bass response with tube amps, which may add up to a warmer than tonally neutral presentation.
As for the sensitivity (85dB-87dB vs. your 40wpc amp), if you are in an average-sized room and don't listen at crazy SPLs, you should be able to drive them adequately. But again, if you listen to a lot of rock and like to listen at concert levels than you are likely going to run out of steam with this pairing. Again, take your amps to a dealer and try them out. That will be the best way of determining their compatibility.
Hope this helps.
"My estimate of the Prince's voltage sensitivity on its tweeter axis was a little lower than specified, at 85dB(B)/2.83V/m. This speaker will definitely benefit from being driven by a powerful amplifier, particularly as its impedance (fig.1) drops below 4 ohms in the mid-treble and above. The impedance rises with decreasing frequency below 1kHz, which means that tube amplifiers, with their relatively high source impedance, will sound heavier in the bass than solid-state amplifiers with the Hansen. But as the Prince V2's impedance at lower frequencies doesn't drop below 8 ohms, this speaker should work well with tube amps."
Here is the impedance and phase angle graph across the frequency spectrum: http://www.stereophile.com/images/archivesart/408Hanfig1.jpg
My suggestion, take your Shindo Sinhonia amp with you to the local dealer who carries the Prince speakers (if you have someone locally) and try them out. You may get a sonic signature that you like but purely from the impedance graph it sounds like you may have attenuated high frequencies/treble and heightened bass response with tube amps, which may add up to a warmer than tonally neutral presentation.
As for the sensitivity (85dB-87dB vs. your 40wpc amp), if you are in an average-sized room and don't listen at crazy SPLs, you should be able to drive them adequately. But again, if you listen to a lot of rock and like to listen at concert levels than you are likely going to run out of steam with this pairing. Again, take your amps to a dealer and try them out. That will be the best way of determining their compatibility.
Hope this helps.