Bar, singular: the Eibach rear sway bar. I can hold curves with less body movement. I doubt that it actually/physically allows faster cornering, but by feeling more "planted", with less tendency to kick out a bit to the side on uneven surfaces, it inspires confidence, allowing me to push harder.
"Float" or "hop" are the objections to the OE rear suspension; because the movement causes that "kick" or "step out" to the side when cornering "spiritedly". I noticed this too though it didn't really bother me much because the recovery was always there; but it really bothers some drivers.
The rear sway bar (set to "soft", i.e. for open roads, not the track) almost entirely eliminates the floaty feel and stepping out when cornering. Also in a straight line, if you hit undulations in the road, the body won't float or hop up and down when it has received the sway bar upgrade: just the initial pop into the air in back and then it settles down without subsequent movement.