If you're are looking for the aroma of spices etc. You'll get the most if you add them after primary because neither your boil nor the vigorous fermenting will blow off the aromatics. However, if you're looking for more of the spice flavor, you might want to add them at the end of the boil.
I've also heard of folks making sort of like a spice essence by boiling the spices in some kind of vodka or brandy or something and then adding the liquid portion into the bottling bucket. Might be another option for you. Try 'em all! See what works better.
Thanks for the input. I will probably make up the vodka concoction and add to the keg. If it works. I'm going to try it again with a wheat as I try and clone New Belgium Brewings Sunshine Wheat.