I use EMT948 which has the same built in phonosatge.
The internal phonostage is guts OK. It sound very neutral but rough and flat. Any decent external phonostage will be better. EMT DD turntable have much more potential that their built in phonostages.
I use the EMT 929 tonearm and TSD15 SFL and SPH carriages. I don't have experience with adapting not EMT tonearms.
Regards,
Alex.