A big part of upgrading suspension is labor, and there is some overlap. Plus you have to worry about getting an alignment for most changes. Modding piecemeal results in a system that is not balanced until you are finally finished. It's not like engine mods (FMIC, DPs, tune etc.) that are fine when done by themselves.
Sway bars are the last mod I would make. Dampers, springs, bushings are more critical. Plus the rear sway is a PITA expensive install. For the street, a decent set of coilovers like Bilstein is probably the most significant change you can make. For another 1k or so you can begin to look at some of the custom systems that HPAutowerks has. Forged wheels & extreme non-rfts are another key improvement.
AcAvenger has an admirable list of mods IMO.