awsmone- I think both you and Alex are technically correct. Soulution only uses a small amount of feedback at a given point, but over a much, much smaller timeframe---so uses it much more often. I think Halcro did something similar, but its been awhile. Its a high negative feedback model in my opinion, but I'm not that technically savvy- perhaps Ralph can chime in here. In the Stereophile review of the 710, graph 4 speaks to negative feedback use (declining distortion as power increases) and there are some higher order harmonics (albeit very, very low in nature).
asiufy- Magico recommends 50w on the 7s, but really after looking at a score of measurements on the Qs and Ss lately, I think 30w SET is a tall order. The Lamm ML3 really runs well at 10w according to the Sphile measurements and then distortion rises well over 1%. Since SETs have rising distortion because of no feedback, you really want to run them at a fraction of rated power anyways I'd think. Also, Magico tends to overstate efficiency. Hifi News in the Q3 review stated the 3 has a pretty wicked phase angle (-71 degrees at 57hz)- and that the speaker is more like a 3 ohm nominal load, not 4. The 7 is probably more like 90dbs adjusting for impedance but likely also has a similar phase angle in the bass since it and the 3 are of similar cloth as I recall. So can you do 10-15w on a 90db speaker with impedance dips in the 2s? Maybe, but I'd want to hear it first- and since the amp costs like 150k, frankly I'd demand it. My guess is 50w P/P probably would work.
I keep coming to Ralph's power vs voltage paradigm on this as well- the Q7 is definitely the latter. I can totally understand how the Dartzeel 108 has no problems with this speaker. In fact, as you probably assume, I'd recommend the 458s and be done with it
You won't need bi-amping and you get all the benefits of a zero global negative feedback loop in a package as fine as a Vacheron watch. But when I hear how the Arbiter isn't tonally correct and the OP wants to do bi-amping because of it, I think that's the absolute wrong direction and trying to correct a deficiency instead of finding something that works in the first place. I haven't heard the Arbiter (not many have), so I can't really be of more help on that side.