Besides the mainstream Pelita and Kayu, the best nasi kandar worth trying are:

Nasi Kandar Zainul, PJ State food court near A&W
Nasi Kandar Yaseen, Jalan TAR
Nasi Kandar Kudu, Jalan TAR
Nasi Kandar Ibramsha, Jalan TAR
Nasi Kandar Fareed Line Clear, Bukit Rahman Putra, Sg Buloh
Nasi Kandar Salam, Damansara Perdana

Any other suggestions?