The tweeter height of your present speakers look to be very low compared to the listening position, at lest from what i can make of the pictures.
The "fuller, smoother" sound could be attributed to a number of things, but that doesn't have much to do with the form factor of the speaker. A bookshelf speaker could easily have the same sonic character versus a tower, it depends on the voicing of the speaker as well as the expectations of the listener, not to mention the acoustic circumstances that the speakers are being heard in.
I get the desire for beefier-looking audio equipment, however. If you can swing the budget for them, take a look at some
KEF Q750s. They will throw out a good sound over a wide area, and can be listened to at a relatively close proximity for a 3-way tower. That is due to the coaxial design of the tweeter/midrange. If you want an imposing-looking bookshelf speaker, check out the
Hsu CCB-8 speakers. They are large and relatively powerful bookshelf speakers that also use a coaxial design.