Synergistic Research XOT Carbon Crossover Transducers

I have them on my Q3s. I had the older model before that. The effect is fairly subtle. More a sort of clearing up of the sound of the speaker and a reduction in perceived hash and noise. Make sure you have room for them, ideally in a combo speaker connection where you can plug the XOTs into the banana socket while connecting your main cables to the spades 

To put things in context treating the cabinets for HFTs had much bigger impact for me. So overall worth trying but do take advantage of the 30 day test offer. 

How much are these ? Is the $450 cover both Loudspeakers ?

Yes, the price is for a pair for two speakers. Each one is terminated with spades or bananas that you connect in parallel with your existing speaker cables