Is a separate phono preamp worthwhile?


Hello all. First post (cherry) for me. Longtime reader.
I have a McIntosh MA8900 integrated with a Ortofon 2M Black for vinyl playback. I'm using the MM input and I'm generally satisfied. I've heard some pressings that sound amazing , so I know it's capable.Would a purchase of a dedicated phono pre add to the performance or should it wait until a future replacement of the cartridge with a probable MC in the future.I mainly listen to prog rock, metal, some jazz , psych and of course classic rock.Thanks. Greg

gjohns
Wait until you go to a moving coil.  The McIntosh MM inputs are considered quite good.
Not any separate phono stage would be better but great many, that's for sure. Unless it is something like Gryphon Diablo integrated's phono stage, separate is a way to go, and even then if you want higher level. Sure, one more pair of interconnects and power cord. Yet, in your case, I would wait because you don't know which MC you might choose. Cartridge first or both at the same time. I think, phono stage should be at least about twice as expensive as cartridge, especially with LOMC. 
I used an EAR 834p with my McIntosh C42 and that was much better than the internal phono preamp. When I upgrated to the C70 I tested for a couple weeks before concluding the C70 phono was better sounding than the EAR. Whatever that anecdotal evidence is worth to you.
Separate phono stages  are a big improvement to built in phono stages for the same reason as power amp and pre amp are superior to a receiver.