You should be fine to use your speakers. According to the Powerpod K12 Plus manual: "When connecting a single speaker to each channel's output, speakers with an impedance between 4 and 8 ohms should be used" (which will give you a combined impedance of 4ohms). Further, the manual shows two Phonic ES152 speakers connected to the K12 plus, and the ES152, like your speakers, are rated at 8ohms/300W.