You have one of the few Time and Phase aligned speakers made in the world. It is also one of the smallest speakers in the Vandy line. So, you shouldn't expect it to 'Rock'. If anything, adding a subwoofer would probably be the best thing rather than changing speakers. Seeing how you enjoy how they can 'dissapear' means you like them, but just need a little more 'oomph'.
As a Vandy owner, you are able to join the Vandersteen website(Just Google Vandersteen). There you can access lots of great information. We love to help all owners.
Bob