I am also currently reading the 3rd volume of 'Saviours of Islamic Spirit' on Shaykh Ahmad Sirhindi (Rahimahullah). I can confirm that there's a section in the book titled 'Rejection of Bid'ah e Hasanah' and also that he was against the Mawlid celebrations (the quote is the same as in the original post by SeekerofGuidance). InshaAllah, if I get time I will try to post some other quotes from the book (if any) which clarify his position further. Wassalam