*mikoboi2009: QD's are used after LSP's to remove left over wax/sealants but QD's are not considered LSP's, QD's are used for quick touch ups only lets say you want to remove dusts and some very light contaminants in the paint. Now as for you question regarding Topcoat, if you're already using Step 3 then you don't have to use Topcoat anymore. Both Step 3 and Top Coat are considered LSP's. So its either you want a carnauba LSP Step 3, or you want a synthetic polymer LSP Top Coat, If its protection you're after then using just one of these would already do the job since layering both these two would not contribute that much to durability and protection based on my experience, but if you're after added gloss and added depth then putting on Top Coat over a coat of Step 3 would definitely give a slight boost to your cars appearance although it doesn't last that long.