Sunder, here is some information for the question -One or Two Subwoofers for Stereo Music System?
Most of stereo systems have two main speakers, yet we have only one subwoofer. Why not two subwoofers as well? In some situations there can be advantages to having two (or more) subwoofers, but in general one is usually sufficient. The reason for this is connected to the fact that, for frequencies below about 700Hz, our sense of hearing measures the phase difference between a sound arriving at each ear, whereas above this frequency it uses mainly level differences. Out of doors, our ability to determine a sound's direction remains quite accurate down to remarkably low frequencies, but this ability collapses when listening indoors. Sources generating low-frequency sounds (below about 100Hz) tend to do so more or less omnidirectionally (the sound wave travels from the source in all directions) because the wavelength of sound is usually larger than the object itself. When a low-frequency sound is generated within an enclosed space, the spherical sound waves created will reflect off the boundary surfaces of the room to arrive back at the ears with a multiplicity of phase variances, due to path-length differences. This confusion of signals makes it impossible for the ear and brain to extract a reliable phase difference, so normal directional acuity fails.
So in theory, since you can't tell where the low frequencies are coming from in a room, one subwoofer will be entirely sufficient. The harmonics of the bass notes will be reproduced by the satellite speakers — which typically start to take over above about 90Hz — and these will provide plenty of directional information through phase and level differences, in the usual way. So, although the bass itself is folded down to mono, the impression of stereo imaging is actually preserved perfectly satisfactorily.
This theory is all well and good, but I often hear people comment that they can hear where a subwoofer is placed in the room. This isn't because of some special acoustic ability on their part, though —rather, it is because of the poor performance of some subwoofers! Designs constructed at a low cost, employing inferior drivers, and those designed to favour efficiency above all else, tend to generate a lot of 'out of band' noise — lots of harmonic distortion and audible port noises, or other artifacts. These occupy the mid-frequency range, which not only makes their position easily detectable, but also obscures and masks the critical mid-range frequencies from the satellite speakers. So adding a cheap subwoofer to quality satellites will actually tend to make the system less rather than more accurate.
A good subwoofer needs to have a very linear driver (which is expensive), an accurate and powerful amplifier (which is expensive), and a well designed and built cabinet (which is... expensive).