DHD isn't a brand I put much faith into but what is the RMS ratings on those subs since I would imagine 500w is most likely the peak rating rather than the continuous wattage envelope...
Sorry to bring up an old thread, but sell the amp. The encounter line isn't all that hot. I've got the powerplant line, which is decent, but I didn't pay more then 130 for either of my amps. I'd recommend selling it and at least go up to the powerplants.
Assuming you want to stick with fusion of course, no reason not to.