I looked through the descriptions and specs on all of the components, and the only thing I can add to Mapman's good comments is the possibility that the bass and/or treble control circuits in the Arcam are either misadjusted or malfunctioning. Have you tried its "direct mode" ("DRCT" on the remote), which removes those circuits from the signal path?
Also, like Michael (Swampwalker), I don't understand why reversing + and - to one speaker would kill the treble, but not affect the bass. In any event, to be sure that the two speakers are in phase with each other verify that a recording featuring a centered soloist results in a well focused image, centered between the speakers. As opposed to an image that is vague, diffuse, and hard to localize.
Regards,
-- Al
Also, like Michael (Swampwalker), I don't understand why reversing + and - to one speaker would kill the treble, but not affect the bass. In any event, to be sure that the two speakers are in phase with each other verify that a recording featuring a centered soloist results in a well focused image, centered between the speakers. As opposed to an image that is vague, diffuse, and hard to localize.
Regards,
-- Al