There are tons of things you could do, but I would start with a drop (best on full coil-overs if you have the $) and then either some 17" or 18" rims. The rims are really dependent on your personal taste, everyone likes different styles and fitment. The Celi definitely takes on a whole new aggressive look with just a drop and larger rims.
After that, for exterior mods you might consider trying some new light housings... 03+ tails, JDM sidemarkers and maybe some different headlight housings if you aren't liking the stockies. The TRD front also looks better with larger fogs mounted in the openings intended for fogs on the outside.
Just my suggestions for a starting point