Dude, I don't think it's so complicated! I'd imagine the various successive numbers are just to designate newer models for marketing purposes. After Sears got the buzzword out, and "everybody" knew what is an HE3 (which rolls off the tongue nicely), the next improved model is a 4. (I found a reference to HE4 and the word "Colors" as a marketing term). Then the next *bigger* and *better* model after that is the HE5. The HE2 is simply a smaller less deluxe model, maybe it's inferred to have "cleaning" and "conservation" with reduced "capacity."