You might consider getting a set of Swarm subwoofers (audiokinesis.com). These are compact and will take care of everything below about 60-70Hz down to 20Hz, with evenly distributed bass throughout the room.
Once you have that sorted (bass is the hardest part and usually the most expensive issue with most speakers) its fairly easy to find a 2-way speaker that is highly resolving and easy to drive that can go down to 50-60Hz. Since bass is omnidirectional below 80Hz (unless your room is ballroom sized or larger) getting it all to blend is easy, and the Swarms won't attract attention to themselves.
Once you have that sorted (bass is the hardest part and usually the most expensive issue with most speakers) its fairly easy to find a 2-way speaker that is highly resolving and easy to drive that can go down to 50-60Hz. Since bass is omnidirectional below 80Hz (unless your room is ballroom sized or larger) getting it all to blend is easy, and the Swarms won't attract attention to themselves.