This is a misconception about this particular model. The 4" drivers only go down to about 120hz or so. Below that the impedance ramps up greatly, asking very little of your amp/receiver, and also providing some degree of safety when using more powerful amps. Plus, the 4" drivers are in their own individual sealed sub-enclosures, with the acoustic suspension/sealed alignment adding even more insurance against over-excursion of the drivers. Even with much greater power, the demands placed on the 4" drivers is not excessive.
120 sounds about right. If the speaker is designed to roll-off at 120(or naturally), seems to me my initial recommendation of setting the receiver to 90-100 would be close. I see no need to tax the receiver/amp for full-range output if the speaker is not designed to go below a certain frequency.
It is my personal opinion that setting a proper x-over point should help clean-up the complaints in the first post of this thread. Adding external amplification should help further.
I've thrown lots of power at mine (NAD C372, plenty of headroom, couple hundred watts or so, full range, two channel system in a large room) and never had any issues. It definitely sounded more effortless than a Yamaha receiver of similar power to the OP's. Mortonconst is on the right track with the Emo amp. Also, the 7006's impedance is below 6 ohms for the most part, with a couple dips to 3 ohms or so, so despite their high sensitivity rating (92db/w/m) they seem to like higher current amplifiers.
I am all for more power. More is better. And, more that is cleaner is even better. In my experience, when you go way beyond what the speaker calls for, the sound remains clean way beyond the speakers limit. Which simply means, one must pay closer attention to the speakers limit, and not the amps.
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That being said, the idea that an amp is just limping along when the speaker is at it's limit is ideal in the right hands. When things still sound clean, I usually push it too far.
