Actually, I don't think it's very difficult to implement a subwoofer into a system but it takes a little planning, experimentation with the sub placement, room size, and dialing in the proper configuration for crossover, volume, etc..
Perhaps most important is a little known secret about syncing up a subwoofer to the main speakers. Some to many interconnects and speaker cables (regardless of price) induce time smear to a small or large degree.
Of course the ideal is to acquire ics and scs that induce little or no time smear. To minimize any disjointedness between the main speakers and the subwoofer, it is imperative that the ics and scs apply similar design methodologies.
For example, if the interconnects to the subwoofer induce much time smear but the speaker cables to the main speaker minimize this time smear, the subwoofer will sound syrupy, wooly, ill-defined, slow, etc. whereas the main speakers' bass will be tight, fast, full, well-defined, controlled, etc.. And there is little or nothing that can be done to remove this disjointedness regardless of tuning, tweaking, and placement strategies you apply.
But when I say it's not difficult, every situation and every room is different, and every sub and speaker match is unique. But there are certainly several things you can apply that will minimize your grief.