The ATI 5670 is similar in terms of power requirements, but offers just a leeeetle more performance from what I've read. Costs just a leeeetle more too.
http://www.xbitlabs.com/articles/video/display/chaintech-apogee-gf9800gtx_8.html#sect3
that's an old article, 9800GT is about 20% faster than 9600GT.
Correct me if i'm wrong...