Not surprising. The Nait has a fantastically musical, addictive character, even if it is not especially linear or accurate. The Planet is also really good at the basics, though not that refined. I can't speak for the Mira 3 directly, but I bet that it is both more hi-fi (revealing, transparent, wider bandwidth, better imaging) and not as good at making the tune and the timing of the music go right to your head.
You may be finding that the greater refinement and transparency of both the new amo and cdp distract you from hearing what you really liked from the Nait/Planet combo.
You may be finding that the greater refinement and transparency of both the new amo and cdp distract you from hearing what you really liked from the Nait/Planet combo.