Sean, the receivers that you've considered are excellent and all provide transparent reproduction. It may be, however, that you're underestimating the new HK635(or upcoming 435). Keep in mind that the power rating of the HK is with all channels driven simultaneously at full power for at least five minutes, while the others, along with most manufacturers, use a rating with two channels driven simultaneously, as permitted by the FTC regulation. Although the two channels driven simultaneously at full power rating is more realistic when considering what happens in the real world of home usage, the difference should be taken into account, which would make the power ratings very similar. Inadequate power for home usage is rarely a problem and almost certainly wouldn't happen with the 635, including at lower speaker impedances.
As far as distortion goes, the differences of hundredths of a percent mentioned are totally meaningless in practice. Testing indicates that in reproduction of music distortion has to exceed 1% or so before it becomes audible. Typical distortion ratings are all far below audibility.
Also note that the 635(and 435)have the new automatic calibration/room equalization system developed by Dr. Toole's colleagues. It's different from others in using both farfield and nearfield measurements and apparently uses the difference between the two as a measure of the room effects, which it then compensates. It also apparently equalizes the sub output so that the lowest bass frequencies, which generally are most in need of equalization, are also compensated. On another board a new owner reported that a bass peak on the order of 20dB was reduced to about 4dB and the overall sound significantly improved after the equalization. Of course, it's your judgment as to whether any of this is meaningful in the light of price differences.
