I will try and simplify what I said.The reasons why the chord progressions at the beginning of Rising Sun sound so good,is the choice of the inversions[the way the notes of the chords are arranged ],the relationship of the bass line to what the left hand is doing on the treble strings
the bass line starts with an A,When it comes to the C chord,the fifth string is fretted 3rd fret with a c notethe fourth string is fretted with an E note second fret,bassline moving upwards,meanwhile treble strings have some downward movement,third string goes from second fret downwards to open third string,next chord is D major,treble strings move up,bassline moves down,this is contrary motion.
if i chose different inversions[of the same chords] perhaps bar chords.
I would not get the same bass line.moving in theopposite

direction to the treble strings chords,so choice of inversions of chords as well as choice of chords is vitally important.
Dorian mode:    A B C D E F# G a. The chords would Am, D major (to accommodate the F#), and Em, with C, Bm (once again, because of the F#), and G as color chords. These six chords contain only the notes of the Dorian mode.
now the above is a very useful explanation,but it goes further than six chords,we have their cega[c6],and bdf#a [b minor seventh],or b modal 7 [bda]now this where open tunings on the guitar can be useful,because in open tunings,we have a little more freedom to double or treble [or quadruple even ]certain notes of the chord inversion,thus altering the flavour of the inversion completely.
I am going to put some links to my playing that illustrate,the importance of inversions,the first is in standard tuning but Ihave made it sound like an open tuning,the chord progressionis e modal,followed by d modal 6 /9 [a d b e no third],followed by d modal[ a d a d a]back to E modal.http://ie.youtube.com/watch?v=ojVFPeU0YQU Dick Miles