if you are looking of strobist stile off camera flash, both the Sigma & the 430 are way more than you need, something like the Vivitar (don't know the model number) or of the the nikon SB 24,26(&28?) are better for the buck.
if you want on camera flash or a flash on a flash bracket, the 430 is a great choice, also another option for ETTL is the EX550. It's a good alternative from the used market, its more powerful than the EX430 but could be had for the same price & it could serve as a master of the ETTL system for later unit additions.
hope you figure out what you want!