One subwoofer can be very frustrating to an astute listener. Best to get at least two to start. Then they are matching. If you can't afford two save longer.
If you use an appropriate crossover they will not color the midrange at all but interestingly give you more sense of depth in the midrange. There is more air in the room. It is an effect that most people notice. Turn off the subs and everything goes flat. But, the crossover is critical and the only ones that offer total control of frequency and slope are digital. People who are married to total analog miss out on this. JL Audio makes a decent analog crossover.
If you use an appropriate crossover they will not color the midrange at all but interestingly give you more sense of depth in the midrange. There is more air in the room. It is an effect that most people notice. Turn off the subs and everything goes flat. But, the crossover is critical and the only ones that offer total control of frequency and slope are digital. People who are married to total analog miss out on this. JL Audio makes a decent analog crossover.