As far as multiple subs go, I would never buy several expensive subs. But I would say, based on the work that I have done and my own experience, that I would much rather have several cheap subs than one expensive one. For a long time I used three $100 subs - worked very well. I did get an improvement by upgrading the subs quality, but it was not a tremendous improvement, noticable, but nothing earth shatering. The biggest improvement comes from the second sub with a little more from the third and diminishing returns from there.

When multiple subs are used each sub need not be all that high performance. In fact I use smaller 12" divers to make the subs smaller, and lower power amps. Judicious choice of RANDOM locations can make them virtually invisible in almost any room, so I don't think that your appearance issue is really a concern. In my theater only one sub is visible all the rest are invisible. The surround speakers are far more obvious than the subs.

And you don't have to be a "rich audiophile" to get the very best sound. But you do have to be willing to make the sound a priority and do things right. In fact, it's not all that expensive to do things right, it's usually cheaper, it's just not what many people want to do. Sound really isn't the highest priority.

For example spending large sums on electronics is a waste of money, but then when you do spend all that money the last thing that you want to do is hide it. I buy the lowest cost electronics and hide it - spend the money where it counts - on the speakers and the room.