FYI, I don't have a K3, but my KX3 drives my KPA500 to around 175-200 W, depending upon band and mode. This is especially useful on 6m, which my Orion II does not cover. On HF and 160m, the Orion easily drives the KPA500 to full power with 30-40 W in. On the HF bands I usually run the KX3 barefoot with a PX3. Lots of fun. 73 Ray W2RS