I think the Subsonic wouldn't be able to keep up with the speed of the Arros (for music anyway). I would look for smaller subs, such as the pinnacle baby boomer or supersonic.. I believe there are some here on audiogon right now... $350 to 450..
Now if music is not a priority, and HT is... then the PSB Subsonic 5i is good value..
Now if music is not a priority, and HT is... then the PSB Subsonic 5i is good value..