Ill help you out since I was in your shoes a few months ago.
3-2-1 headers give more low end power as oppose to 3-1 headers which give more top end. Pending on what you would rather have its totally up to you. I have greddy 4-1 and they have good top end. Far as the strut bar havent installed one myself yet but it should bolt straight on if you ordered the right one. where did you get your bar? for how much? I need one too.

L8