I agree with many comments here but I will say after running 300b's for a few years and having to retubing my amp I wish I gone el84 lol.
I have very good transformers in my amp hashimoto's and do not feel I'm missing anything( over other tube verities) in the bottom end or top end, I have efficient speakers though 94db and 99db.
I ran the 300b's on those 94db speakers for a couple years made great music but they were limited to lower listening levels so IMO your 89db speaker wont be a great match, doable but not satisfying IMO.
also 300b's are getting very pricy compared to el34's I spent $800 this summer on 2 new gold lions, and another $700 on small signal tubes (2x12ax's and 2x6sn's). keep that in mind every couple years buying 300b's gets expensive fast, specially if your pushing them with low efficiency speaker they will go faster.
I have very good transformers in my amp hashimoto's and do not feel I'm missing anything( over other tube verities) in the bottom end or top end, I have efficient speakers though 94db and 99db.
I ran the 300b's on those 94db speakers for a couple years made great music but they were limited to lower listening levels so IMO your 89db speaker wont be a great match, doable but not satisfying IMO.
also 300b's are getting very pricy compared to el34's I spent $800 this summer on 2 new gold lions, and another $700 on small signal tubes (2x12ax's and 2x6sn's). keep that in mind every couple years buying 300b's gets expensive fast, specially if your pushing them with low efficiency speaker they will go faster.