You know, these speakers are pretty good. The price is a killer for the quality you receive. I bought these for my second system. I did not want to spend $4000 but, I wanted a decent loudspeaker that wouldn't massacre the signal. Now, they are no match for the Gemme Audio Katana's in my main system, as a matter of fact there are not many matches against the Gemme's. Of course the Katana's run $15,000. In listening to the 400's I found the first impression to be lean and somewhat muddled in the mid's. This effect was of course due to the break in issue. I would expect the break in time to be about 100 hrs. After this point the sound relaxed appreciably while bass and mid control improved. The highs never had a shrillness or edge and I would say the highs became more focused but imaging expanded after breakin. The bass projected by these speakers is impressive and it remains tight and controlled. These are not BOOM-BOOM speakers...if you want that go with Cerwin-Vega's, the ultimate "I don't care what they sound like, they rock" speaker. I measured 44 hertz which is quite respectable. For $600.00 a pair you cannot go wrong. Polk has always had a certain house sound. I remember this sound from the 1980's and 1990's and the sound has not changed much in 25 years which is a good thing. This indicates a dedication to preserving the design parameters of Matthew Polk. Polk's have been a good imaging speaker and these are no exception, but what I found to be very interesting from models I had heard in the past was a change to the soundstage. The 400's, and I would assume the other speakers in the line, present a three dimensional image that many speakers at 3x this price point do not. I could here a fairly seemless transition within the drivers, no drops or ridges. I would guess that the response is pretty flat. I could place instruments within the soundstage. Voicing was front and center. Speaking of voicing, the 400's presented a natural full throated voice without nasality or tonal shifts. I would suggest using a very good amplification source. A $500 receiver just won't cut it with these and will not allow the 400's to live to their potential. I ran these with a Creek Destiny and good amplification does make a difference. Bi-wiring is a personal decision. On some speakers it is a necessity, with some others it is not. If you can, try it with the Polk's. If you want a speaker that provides a very good reproduction platform these are it. Better then Kef, Klipsch, Infinity, and Boston....at this price point. It would appear that Polk still cares about music production and aims for a high end sound at a low end price. If you want a little more bottom, try the 500's. But, sometimes the top of the line speaker (within the product line) does not mean you get better re-production, speakers tend to be finicky and this speaker really brings it all together in the right way. Thanks.