SB-1000 will be a significant step up in sound quality but as a small sealed sub it's way under powered for primarily movies in a 2800cf room. I would look at ported subs. If your budget is in the $400-500 range I would look at:
SVS PB-1000 (unfortunately no more in outlet)
Monoprice Monolith 10
RSL Speedwoofer 10S
Hsu VTF-1 MK3
Hsu VTF-2 MK5