I've listened to many of the Thiel models and most of the Dunlavy models. I wound up buying the SC-V's after listening to the SC-IVA's. Not to say that I didnt like the SC-IVAs. Then I moved up to the SC-VI's, my present speakers.
Now speaking of the SC-IVA's
.. Someone else compared them to an electrostat and I agree, there is nothing quite like the sound of the symmetrical vertical array of the Dunlavy's. I felt that the Thiels that I've listened to were too bright (so I agree with Ejlif who stated the Dunlavy's are a bit laid back). To me that equates to the smoothness of the Dunlavy's. I also felt that the Thiels didn't have the bass definition and authority of the Dunlavy's (IVA, V, and VI).
They ARE big and heavy and require a larger room size. But, if you have the room, the Dunlavy's coupled with the right electronics will fill it with music effortlessly. I also agree with Czbbcl that you may wish to consider upgrading the preamp too.
You owe it to yourself to go listen the Dunlavy's if you can. Happy listening!!