I love the MP11SE. I went through a Nord Piano 3 and Stage 3 before I got it. The default grand is the best piano I've ever played, including in real life, and the pads and strings are very nice, superior to the Nord Piano and Sample library. It feels and plays like a grand, has a triple sensor keybed and ivory feel keys, and there's 256 voices of polyphony. I was learning Moonlight Sonata when I upgraded and it was a night and day difference playing it on the MP11SE vs. the Stage 3. It's not playable on the Prophet X (not enough keys, too much polyphony, and it's all sustain).
It's also a reasonable four zone MIDI controller, which I wasn't expecting, and even has a built-in recorder, a USB thumb drive slot, and a metronome. You can tweak almost anything about it, including custom curves:
http://www.kawai.com.au/pdfs/OwnersManuals/Kawai%20MP11SE%20Owner's%20Manual.pdfOnly downside is weight but mine's in a home studio and never leaving.
I am trying to learn classical piano. I have the synthesizers for fun. After the Moog One, the only other gear I want is a quad Buchla 200. I'm happy with everything in the studio at the moment. I'd still vaguely like to try a Linnstrument or a Madrona Soundplane, but I have the Push 2, so I'll probably ignore that urge. :-)
Good suggestion about moving the Prophet 5 patches. The 8Dio add-on sounds amazing through the stereo filters. There are bugs still, I can't seem to get it to save the current patch if I'm in the add-on. They categorized all the Prophet 5 sounds, so you find them through the Sample section. It's unclear what they're using the programs for, the manual is light.
Prophet 5 manual:
http://synthfool.com/docs/SequentialCircuits/Prophet_Series/Sequential%20Circuits%20Prophet%205%20Owners%20Manual.pdfI noticed after I bought them that there's a 10% discount code in the forum, so don't miss that!