PFR Quad 99 Yamaha NS 200m

Dear all,
I just got a pair of impresive Yamaha NS 200M monitors. I am very happy, but for the fact that I can´t move the volume of my Conrad Johnson PFR preamp from 7 in the dial (zero volume), to 8 even, because the speakers are about to explode. I´ve been looking at the posts in Audiogon and it would seem that the Scott Endler attenuators could be of help? Any and all comments will be greatly appreciated.
-- my amp is a Quad 99.
Thanks!