You can strip away the ReplayGain in Foobar2k. Feel free to do that if you wish.
DR meter results are no different with and without ReplayGain. Someone more qualified will have to answer if it actually changes dynamics. I have never heard objectivist audiophiles say it does that.
If a file simply has a replaygain adjustment number associated with it as a tag, for use when Replaygain is set to 'on', that can be overridden simply by leaving Replaygain set to 'off'.
But if the replaygain suggested volume adjustment was hard-coded, you can't strip it simply using foobar. You have to manually re-adjust the levels back to what they were originally, whatever that was.
These files have had the replaygain adjustment hard-coded. They all play at the same perceptual level. (this is also demonstrated by the fact that first, they re have no replaygain tags, and second, when you run a replaygain scan on them, the suggested volume adjustment for all of them is 0 dB) There is no easy way to override it. Nor should you, really, if you want the keep the comparison fair. Otherwise 'quality preference' is influenced by simple overall volume.