I have recently upgraded my amp to a Yamaha DSP-AX750SE so I'm reviewing my set up. I am using KEF Q35s for the front speakers which have a pretty meaty bass anyway, so up to now I've lived quite happily (ignorantly?) without a sub-woofer. I have a few newbie questions to help me make a decision: 1. Will a sub make a big difference? 2. Would the the BK XLS200 be a reasonable choice in this system? 3. What is the real difference between forward and downward drive? I would only be looking to attach the sub at line-level and hide it a few meters away from the amp and tv (and the wife!) down the end of the sofa. I live in an upstairs converted flat so I do not want a lot of noise escaping downstairs. I would probably only use the sub for movies. Thanks in advance.