You could use the digital version of the 645, the HS5645 - its rated at 164inoz and 0.18sec vs the 645 at 133inoz and 0.2sec. Both are MG and BB type servos. Its $47 from TH. I use these and they've been a reliable servo.

The next step is a 7955TG at 333inoz and .15sec, but thats $120.