Subwoofer location
The SVS and HSU subwoofers can perform best if you allow some flexibility and take the time to determine the optimal location for the sub. As you move it into a corner, it will increase the bass output and can effect room modes. For this reason, a regular sub should not be mounted in a wall or cabinet.
If the size of the SVS and HSU 12" subs is too big, consider a 10" model which will compromise some performance for asthetics.
There are also some subwoofers that are designed to be mounted between the studs in a wall, but in the same $600 price range, they wont deliver near the performance as the SVS or HSU subwoofer and will probably require an external amplifier.