To get good sound you need good stands...the stands take up floor space, maybe not as much?...depends.
I have always found better integration of treble/mid and bass with floorstanders as opposed to a satellite/sub combo. You also save the expense and clutter of interconnects. As far as space goes, the footprint of my current floorstanders is the same as the stand mounted speakers I used to have. In fact a stand mounted speaker, plus a sub, may take up more room than a floorstanding speaker because of the extra space rquired by the sub. Also, you mentioned that you use your system for HT. A good floorstanding speaker may give good bass for HT effects. You don't necessarily need to add a sub. On the other hand, if you have small bookshelfs, the sub will also be small. In effect, it will be a woofer for the small speaker, rather than a true sub. It seems counterintuitive, but you may get better bass for HT with a floorstanding speaker rather than using a small satellite/sub combo.