1 Subwoofer or Are 2 Better??

The answer could be dictated by your particular rooms acoustic signature. After adding a second sub in my HT space My Pioneer's room correction easily displayed the difference with its on screen EQ display. Honestly, I couldn't hear a significant difference in this room. I did notice a significant difference while at another location in the house.

So, in my house the answer is, defiantly maybe and yes. IMO for now it wasn't worth the expense but I'm not taking it out. I'm betting the audio quality for mass media will soon improve to a point where it will take full advantage of the current hardware. The quality is there the problem is post production and the medium.

Sure two would be better. Four would be better still. It comes down to how much to spend and place to put them.
I bought one JL F-113 Fathom sub and it is awesome.
Again, two would be better... 2 costs twice as much, and I am not sure if I have the room for one more JL sub.
I use the JL sub with my Stereo system.

I also have 2 more subs (Outlaw Audio) for my Home theatre which is loacted in the same room with my 2 channel set up.

I think I still have a M&K 250 Watt 2-12 woofer sub if anyone is interested.

I found the Harmon paper interesting, although I think there was little new that I didn't already know, but it is a reasoned explication. Bottom line is that one well placed sub, often corner placed, is usually all you need unless your room is very large. As the series of papers notes, lots of unsubstantiated mystic in audio.

db

I also have a JL Labs Fathom 113
I don't feel I'm missing anything
although some year I may add another

this is in my HT room

my 2 channel room doesn't need subs