Krell fpb 600 svs ultra tower

Hi guys I have a question how loud (db) should a Krell fpb600 get with Svs ultra towers get I have I hooked up sounds amazing low volume and all the way up. Using Amazon music which seems very low but would have thought it being a 600 watt amp on 8 ohms it should be way louder. But all the way up and still sounds clear thanks