I ran my hk1998 at .7 for two years just fine that was a 2ohm min amp...I have ran my hk4000d at .5 and .7 fine for years as well.... Ask ppl who own the amps first then others. What series is the amp. Mostly what ma audio will tell you is to keep the voltage up and you'll be fine. Thats what they said about my hk1998. I think that amp is two years old now.