GR2 are stock shocks, possibly slightly stiffer. you want AGx's or shortend koni struts.
you can not lower the b14 any lower than 1.5 inches without problems of bottoming the suspension. you need high spring rates of 300lb front and 250lb rear. you have 2 options, 1 would be hyperco's only bought through sr20forum in a group buy. or 2. ground controll coil overs with 300lb front and 250lb rear, these you can adjust to any height you want but i still wouldnt go lower than 1.5inches.
read
www.sentra.net
the best thing to do if you want a low stance is get some shortend koni struts made by steve on sr20forum and put hypercoils on the (i beleve the shortend struts have a lower perch so that lowers your car as well) or go full coil over (i.e. tein SS, tein basic, progress, D2)