8 pages per day sounds like pretty good to me, but I don’t know any of the three books, so I cannot compare…
If I were in your position, I would actually sit down one day and try to read the first few pages of the two books. This way you can find out (a) how you get along with them in terms of difficulty (I have abandoned books after 2 pages because I just couldn’t make sense of anything) and (b) how your reading speed compares to what you‘re used now. That should give you solid data to base your decision on.
) But if you can find a copy of that other book and you don’t mind the Furi, then that’s even easier!
)
そうしゃ is the current reading, but そうじゃ seems to be a reading from the Edo period or so? If you follow the Wikipedia link given for 奏者番 it mentions both readings.

