Steeda, Maximum Motorsports. MM probably has the best around IMO, but you are going to pay a little bit more.
Why are you upgrading? What else have you upgraded on your suspension to make you want to upgrade the sway bars? From most people, new bushings and end-links will do it.
Rear sway bar from MM:
http://www.maximummotorsports.com/rsb.asp
Steeda has some tubular from sway bars.