I'm assuming that you mean by "must go low" in frequency as opposed to playing well at low volume. I think you'll find that your room will be more of a challange than your search for a suitable speaker. You might want to consider something like the TacT gear to facilitate your desire. Speakers that might be worth considering include the Vanderstein 5's, the Gradients or something like the Thiel sub-woofers.
Full Range Speakers for a Small Listening Room
Do they exist? I listen primarily to classical music in a small dedicated listening room. The speakers must go low. The dimensions are 11 ft wide by 16 ft deep. I currently sit 9 feet from the speakers. My budget would be limited to $10k. Assume I do not have any amplifier restriction. I would be willing to re-do amplification if necessary. I would build a new system based around the speakers. Thanks in advance for your thoughts.