My guess is that the 350W/600W 8 ohm/4 ohm mono ratings, which are shown in the manual and in the fancily printed part of the brochure, are accurate.
The white spec sheet showing 200W/400W, that is part of the brochure pdf, I suspect is a document that is earlier and preliminary. I say that based in part on its look, compared to the other documents. But note also that it specifies S/N ratio as "more than 100 db," as if someone made up the spec before they had more precise knowledge of it, while the other documents specifically indicate 128 db (although the reference level isn't specified).
Also, peak vs. RMS would not account numerically for the disparity between the two sets of numbers. Unless perhaps "peak power" is interpreted to mean "dynamic (short term) RMS power," or more precisely "dynamic (short term) average power." But that would make the numbers that are presented for stereo and mono modes completely inconsistent with each other, and be very misleading. I very much doubt that Classe would specify things in that manner.
Keep in mind, also, that potentially/ideally a bridged amp can output four times as much power as when the same amp is operated in stereo mode, since the output voltage swing capability is doubled. Although in practice the 4x factor usually comes out to be significantly less, due to current and/or thermal limitations.
In any event, given the impedance characteristics of your speakers you should be fine either way.
Regarding question 2, I wouldn't be surprised if the sensitivity increases by 6 db (i.e., you would have to reduce your volume control setting by 6 db, to achieve the same volume as in stereo configuration). But without being familiar with the details of the design, I don't think we can be certain of that.
Regarding question 1, I wouldn't want to venture a guess as to how the sonic differences would net out, without having tried it on the same or similar models, and with a speaker having similar impedance characteristics.
Regards,
-- Al
