The 15-200 watts spec gives a range of RMS watts the loudspeaker will adequately perform. If the spec is accurate, for it might not be, you could use up to 200 watts of continuous power with this model loudspeaker.
By reputation the Boston Acoustics VR series are good loudspeakers. As with all older loudspeakers they may need work on the crossover components and the tweeter's ferrofluid.