I made a post few days ago about 990 being too harsh to my tastes with my Paradigm 100s. I was comparing the sound in Stereo (990s DACs) and Bypass (Wolfson WM8740 DACs of my Cambridge Azur CD player) and the sound is distinctively different - 990 is much brighter sounding when the Azur is more smooth and laid back. I think (at least that's how I hear it) that the 990s DACs have somehow subdued sound in mid-lows (around 500-100 Hz), and that makes the sound a little skewed to high frequencies (3KHz and up). When trying to play louder, it makes it hard to listen as SPLs at these frequencies are too high comparing to mid-low range. At low range it picks up again, but to me the overal soundstage is not smooth - there is a gap in levels between mids and low end. Again - that's what I hear. Maybe my ears are weird On the other hand, the Azur does not have this effect.

Anyway, here is the deal. I hooked H/K 635 yesterday evening to the 7700 amp (of course made the settings similar to the 990 and calibrated) to see if I can live with it and return the 990. The short answer is - no. Here goes the long answer.
The 635 does sound somehow smoother. The overall soundstage is much more balanced, with lows, mid-lows, mid-highs and highs playing with about the same perceived levels. No overloaded mid-highs and subdued mid-lows. For example the vocals are extended lower comparing to the 990, female singing sounds fuller.
So can 635 compare to the 990? Not really. The sound of 635 is not as clean. Comparing to 990 it's kind of veiled and muddy. Subtle details in music, which 990 resolves effortlessly, get lost with 635. The biggest problem is in the low end - it's not just muddy, it's mud itself. The 990 is very detailed in the lows, for example listenning to bass guitar is a pleasure. With 635 it's even hard to follow the bass guitar as it's becoming some indistinct rumble. Also, the 990 goes a lot lower without losing the clarity of bass. I can actually hear the subwoofer play note by note with 990, when with 635 is more like just some muddled low-frequency effects.

Conclusions of Part 1. I wish the 990 had a more even soundstage without losing the details. 635 goes to eBay. I went to a local store and picked up an Arcam AVP700 on loan. It's sitting on the floor ready to be hooked and calibrated. I will spend today and tomorrow listening to it and the 990. I will not be able to do a blind test or any kind of scientific comparison, but it's not my goal anyway. I'll just pick one that will give me more enjoyment with music. I'll let you know how it goes.