I wouldn't hesitate moving to a 170, unless there is something in it that will eat the pearsei.
I must admit though a 170 is quite small for pearsei, my trio outgrew a 150 in about 2 years and were moved to 300 gal rubbermaid tub (as normally gentle giants that they are, they get belligerent if cramped in in too small a space), and in another year, the 300 was too small, with them ending up in a 1000 gal intex pool.
Same thing happened with bocourti.
Luckily my son went off to college, and his room was the absconded for the indoor pool.