you can use i386 for sure.
basically cuz you already are using red hat 9, it won't make a difference what architecture you use (i3,4,5,686).
red hat is not optimized whatsoever for your box, it will be slow compared to something like Jamd (based on rh9) or gentoo or lfs.
do NOT use the src ones unless you plan on recompiling them first.
see the below links for more details