Din, keep in mind that you're mentioned modes which have different effects. Processes such as DPLII(x), Logic 7 and Neo:6 extract ambience naturally present in two-channel recordings and steer it to the surround channels where it belongs, to give a little more realistic effect. This is relatively subtle, however, and the surrounds aren't supposed to have nearly the loudness of the mains, even in recordings which have a lot of ambience to extract.
On the other hand, "all-channel stereo", "seven-channel stereo", etc. simply duplicates at equal level the front channel in both the side and back surrounds on that side. This isn't a natural effect, but can be useful for parties, etc. Your 630 has a seven-channel stereo mode which may be what you called "7.1 stereo" which should have the side and back surrounds playing the front channel at equal loudness, assuming proper calibration. Re-check your manual, but with the correct settings for seven speakers and seven-channel stereo mode you should have experienced this.
