Sorry, this was typed in bed on phone. You are correct the WA7 will not drive the HE-6 to its potential. Your Marantz integrated may be fine for the time being. I used a 20 wpc integrated Xindak Class-A, which was fantastic, particularly for the price. Eventually, though, I craved more power and realized things could be better. And I still can do better. In other words, for now, you'll be alright. I mentioned the AHB2 because it possesses the transparency and power worthy of the HE-6, although not cheap and dependent (as usual) on a good pre-amp. I myself do not yet own one. A First Watt amp, already mentioned, is similarly worth looking into. Best of luck!