Oh, and I forgot. First, that D20E above should actually mean D20E MkII. Well, and the N15 is an entry-level spherical with pretty high compliance, while the NF15XEII is an entry-level, medium sharp elliptical with a bit lower compliance, whereas the D20EII is a higher quality, medium sharp elliptical with nude diamond and also pretty high compliance.
Greetings from Munich!
Manfred / lini