My DefTech's are rated @ 4 to 8 ohms, with most benchtests showing they are around 5 ohms most of the time.

I think they are exemplory amplifiers. And I think they can handle any load with ease. I listened to music and movies at reference levels at times and there was never any harshness.

I dont know if the speakers or preamp are contributors to that, but the 200's are a fine amplifier. I wouldnt worry about 4 ohm loads. Then again, I wouldnt run a speaker thats rated at 4 ohms, for 10 hours straight, on a hot summer day. Other then that, no need to worry

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Play it LoUd!!