Chances are if it does have the ability to play 4 ohm loads, it can handle the ER series fine in the standard mode you're using. If it did have any issues, it would likely trip the internal protection mode circuit and automatically shut off before any long-term damage could be done.
I can't comment on the ERM-1s, however I have the ERD-1 surrounds in my main HT setup and they are extremely impressive. I've had the Axiom QS-8s and Boston Acoustics VRX surrounds, both in their own right good surrounds and for the money, these are wicked performers.
I had favored the QS-8s for a while, however having owned the ERDs for some time now and having had the opportunity to play them will all types of sources, I feel these are equal or even better than the Axioms for music as well as movies. I've yet to hear any sort of compression or distortion, even at extremely high volumes.
If you did have issues with the load and felt you couldn't keep them, Emotiva does have a 30 day money back return policy, so you'd only be out return shipping, which would be relatively minimal.
I don't think anyone out there can beat the ERDs for value, and that's at their original price of $350. For their current going price of $249, they are even better... -TD