Sfar and I have "conversed" before about the 5.0's. I have not heard the ProAcs, but I can tell you that the way I have the 5.0's set up its hard to imagine more low level liveliness than I'm experiencing in my room. I returned the Soliloquy custom stands because they just killed the dynamics. My favorite setup so far is Lovan Caliber stands filled with a small steel shot and sand mix with the speakers sitting on cork. With that combination I hear everything on the recording, especially extreme bass definition that was always buried. I'm constantly amazed. Try the 5.0's in your listening room if you can...
Chris
Chris