Add a sub and they sound just as big as a floor stander.
This is pretty much what I have found.
I have some incredible DIY (with close to state of the art drivers and x-over), sitting on a woofer module, and they sound as big as any 3 way floor standing speaker.
Now mind you, the woofer module is NOT a subwoofer, it is a true woofer. The 2-ways are being crossed over at 200 hz, and the 10" woofer module takes over from there.