If you're going to spend money on getting mufflers anyway, why don't you just kick in the extra couple hundred and get a full cat-back, like these guys are saying? I'm sure if you look around some of the 350z forums you will eventually find someone selling a used exhaust. Try looking around these sites:

www.my350z.com
www.350zmotoring.com
www.350z-tech.com
www.350zfrenzy.com

As far as a good sounding exhaust, from the clips that I've heard, both the Borla and the Injen SES sound very good. Supposedly no rasp, not ricey at all, and they're both true dual exhausts...dynos shown at about 13hp/13tq gains for both exhausts.

Or you could take the money from exhaust/y-pipe/headers and just man up and get a Nitrous Express wet kit