Pay the nay-sayers no heed: if you want to get the very best performance from your hi-fi kit, decent speaker cable is a must.
Still, £131 for two 3.5m, terminated lengths (I.M.P. doesn't list a price per metre) is fairly steep, so you're perfectly justified in demanding a significant improvement. The trouble for I.M.P. is that though the Black Knight Extreme cable is decent and very well made, it doesn't do enough to justify the price.
That said, the sound it delivers is by no means bad. Detail levels are reasonable, rhythm carries through unhindered, and the soundstage is open and fairly expansive. The problem is that, while the music drifts over you without causing offence, it also rather fails in creating excitement.
This is mostly down to dynamics. The grand crashes and bangs of an orchestral score are present, but the low-level dynamics and fine details that create anticipation and drama are sadly lacking. It's this that makes the I.M.P.'s overall listening experience just a little dull next to the competition.