One sub would work but it is a pain. I have two and had both break (failed volume pots) so I had one sub for a few months as I rotated them out for repair.
After a few days of messing around I got it to sound good in the prime seat with one sub but I was always messing with the volume. The dips and peaks were bigger in my room with one sub so 30hz would be too loud and 60hz would be too soft. So song to song seemed off sometimes.
After a month or two I had two working subs again. Dropped them down and everything fell into place. More balanced and just seemed right.
You could always start with one and add another later. I am sure you could fine somewhere with a 60 day trial. Music direct ,Crutchfield, SVS has home trials too and I am sure a bunch of brands do these days.