Well I the DFs are 10-15% stiffer than stock and the NFs are 5-10% stiffer, so if you like the NFs but still want to go lower, grab the DFs. the ride won't change too much and you'll get the lowest drop around without bags or coils.
The hotchkis springs also give you a low low drop but they are VERY stiff. They turn your xB into a tank. Ive had these on an xB and it was rough dude.
I would have got these on last weekend but the package didnt arrive in time, now Im going to chicago for a week tomorrow so I gotta wait till the 11th to put them on!