The interesting thing about the Proteii is that each model was meant for a specific genre. The first model focused on pop and rock (hence, its use in bands like Genesis), while the second goes down in history as being the first synthesizer to focus on orchestral music (unless one counts the Roland S700 series that had a mostly orchestral factory library).
The Proteus 3 modules focused primarily on ethnic music. The Emulator II classics (the waterphone and the shakuhachi) are represented as 16-bit samples, but there are quite a few other instruments as well, including even some electronic waveforms that also appeared in the Proteus 1 and 2.
It appears the Proteus 3 may not have sold well, though, relative to the prior two, as I didn't even know there was an XR edition until I saw the eBay listing, not to mention Emu's bundle modules focused on the first two, namely, the Proteus MPS+ keyboard (used exclusively in the Myst soundtrack), the Proteus/1 plus Orchestral and even the ProteusFX.
I hope to make a video demonstrating the rare XR patches in particular of the Proteus/3, likely before my Fairlight Series III rebooot video, as that's still taking a while to make decent Kontakt instruments.
Which also reminds me: I should get more cables for my new toy.