Roger&Me
Bluelighter
[etc...etc...] Now when you look at MDMA/MDA, you have that dimethoxy bridge focusing a giant chunk of the structures electronegativity to the benzene end of the molecule. I imagine the bridge as being a sort of 'knife' or more like a better fitting ligand to serotogenic receptors, and as a result, the star of the show is now the empathogenic character brought on about the increased affinity to those receptors responsible. [etc...etc...]
Not even trying to be rude at all, but your understanding of stimulant and entactogen SAR seems pretty half baked. Bridging the dimethoxy only serves to change the orientation of the m-oxygen's nonbonding electrons, so that they lie anti to the 4-pos. That, in turn, changes the binding profile from a 5-HT2A agonist (e.g. 3,4-DMA) to a substrate at SERT/DAT/NET (eg. MDA).