Yes, my experiences with this are similar. But since I haven’t yet tested that online/offline switching (which is what the XA2U uses), I’ll give it a try and see if it makes any difference (power-wise, because impact on performance is clearly noticeable).
Indeed. If this online/offline thing doesn’t make any difference (and I suspect that it doesn’t) then there’s something else than any CPU-related things eating that much energy, and we won’t be able to do anything about it.