Yep you just need a good powered sub. I use a Klipsch sw308 with my ls50s in a 12x12 room and it does just what you describe. Room size matters. Personally I would not recommend ls50s for larger rooms. They are just too small even if augmented by a sub and have to work too hard. But in a small to modest size room within their limits they are very good. Also you need a beefy high current amp for ls50s in any case otherwise you can lose a lot.
id say start with one especially if you mostly listen in a particular sweet spot. It can be adjusted for that. Multiple subs would be for smoothing out bass response across the room if that is a concern.
id say start with one especially if you mostly listen in a particular sweet spot. It can be adjusted for that. Multiple subs would be for smoothing out bass response across the room if that is a concern.