First, let me correct something here. The RD 2000 has 8 independent zones (which means, you can play up to 8 patches/sounds at a time, and adjust each of them independently). But you can combine even more than 8 at a time with a DAW of course.
It does not need built-in speakers... why? Because it is a Stage Digital Piano; it was designed focused on the professional use. But despite being marketed as a digital piano, it does has the power of an extremely powerful MIDI controller, bundled with extensive MIDI features, including combinations and scenes, great DAW integration with a built-in audio interface at 24bit/48Khz, and it has more than 1,100 non-piano sounds, including organs, synths, brass, orchestral strings, and many others, plus the expansions. And gorgeous pianos sounds (which for me is a top priority) and many great other sounds. In fact, this is much more than just a digital piano.
But one of my favorite things about the RD 2000 is the authentic hammer action and escapement; this keybed captures every nuance of your expression, you can feel how this piano reacts to your expression as you play. It is the Roland's premium PHA-50 keyboard action which other than a real grand piano, the RD 2000 is the one that has given me the most satisfactory action and feel. This includes an advanced sensor mechanism which makes it incredibly responsive to acoustic and electric pianos
The piano sounds are gorgeous. But I recommend you two things to have the same happiness that I have with this piano: 1st, install the latest system update from the Roland website. 2nd, learn to create your own (custom) piano sound; it's easy and there are instructional videos online to help you. Why? Because your idea of how a piano sound should be, is different than my idea, and anyone else idea. Everybody has a different preference. But that's one of the great things about the RD 2000, it does gives you an easy way to create your own dream piano. Both, the V-Piano Engine and the SuperNatural sound engine, both are amazing. Try it!
And there's a lot of features and good things to say about this instrument, but I don't want to make this review longer.
If you are a pianist, your top priority is the piano sounds and the action/feel. This instrument gives you that, plus the MIDI and stage/performance features.
In a few words: When I bought this piano, I was just trying it, but then I couldn't resist to this instrument, and I keep it. I was so amazed of everything! Roland made a really great job with this instrument. I love it forever!