Are the JL Fathom subs really that good....

If you place one sub in the same plane as the main speakers you can't tell where the sub is, assuming a 60Hz 12db/octave crossover. If you place the sub closer or farther from the listening position than the mains you may have to adjust the arrival time (which is tricky stuff).

Bass sounds are omni-directional, but in a car the shock waves through the structure of a car aren't, and that's why you can tell where the sub is. Even in a house I can tell that the bass is coming from somewhere in front of me, but I can't discern the sub's position between the speakers. Or even that it exists.

Still, I have to agree, two subs are better than one, and optimum positioning seems to be one near each main, assuming that's a good position considering room modes. (It often isn't.)

Bass may be omnidirectional but that doesn't mean you can't localize the source. I think that would be called "omnipresent". Like when my wife spots an audio purchase on our credit card online statement within minutes or hours of a new transaction.

Yes they are very very good and very fast.
There is no problem integrating them into a 2 channel system, it just takes time and more of it if you are using 2.

I bought one f113 and it took me close to 10 weeks to fine-tune the position, cross0ver points and phase (plus break-in) and all I can say is these are the fastest and best subs I've yet owned. Prior to this I had 2 REL Stentors and had issues with reliability but these JL's seem to be built like a battleship!
(Dealer disclaimer - not for JL at this time)

Bizango1, if bass is omnidirectional, and that's a physical fact below 100Hz, then by definition you can only localize a source by means other than listening. :-)

Bass is a funny phenomenon because you feel it as much as you hear it. Your sense of touch does not work like your ears. Hearing is logarithmic. It takes a doubling of power to produce a small difference in apparent loudness levels (3db), yet as everyone knows a doubling of mechanical force feels like a doubling of mechanical force. So a 3db increase in sound level at 40Hz can result in a feeling that you've really turned up the bass, because you're feeling it.

Regarding JL subs for 2ch audio, the only thing that kept me out of an F212 was that it didn't have a high-pass filter for the woofers on the mains. All of my demos of various subs I did revealed that unless you use a high-pass filter, preferably at about 60-80Hz, the bass sounded muddy and over-blown. Yes, I know this is a highly controversial point. Some folks like that bass-heavy sound, but not me. I looked into a Bryston 10B-SUB to perform bass management, but F212 + 10B-SUB = big bucks. I just got a Velodyne DD18+ instead. A pair of SVS SB13-Pluses are also a good choice for music, and include high-pass filters.