the pulleys are highly recommended around here. check out
http://www.unorthodoxracing.com/infiniti_g20.html
you should go with the 2 pulley set instead of the 4 pulley set. the reasoning is if you have an aftermarket stereo, which you obviously do, you should not replace the alternator belt. also the 2 pulley set is a lot cheaper than the 4 pulley set, obviously b/c you get less pulleys.
i would recommend getting pulleys before a header b/c they're cheaper and a great mod. then i'd get header, then short shifter.
if you want more info about pulleys check out
www.g20.net there is a section about pulleys. also you could do a search here on AF.