Bass is the backbone upon which the rest of the music rides on. Up until the mid 80’s subs weren’t needed. Then the Mfgs etc started pushing midrange because it has the majority of the music.R&Rollers weren’t considered in this because classical and jazz were the accepted genres. In doing so, they robbed the bass from the speakers so that now, even a supposed full range speaker needs a sub for life of the music. It took me a while to accept that but i have run subs for 20 yrs and choose Rel as THE sub IMO. As has been said, pairs are better and the Rels add so much more to the music, IE sound stage and make the speakers sound bigger.And they are very easy to integrate. Depending on your room size, there as a Sumiko S10 for sale which is the Rel S5 clone. It operates in the same way as Rel and Suniko was the distributor here in the US for many years.and somehow pretty much copied the Rel ,,, at least for a year. .
BTW no affiliation with the seller. Just familiar with them and have them myself