LLiddell, not to be a wise guy, but in my case I too "only was looking for 100 hp extra" and got some Mach 1. 6s, of course this was until I felt what that was like then . . . well see my sig. If I had to do it over, I'd go big first. I got lucky and was able to sell my initial 1. 6s to another member for a sweetheart deal for both of us (which included his stock injectors being sent to me for cores on the new 5s I went with) he was happy with their results and I was happy with the deal we made, but I could have been stuck with the 1. 6s and then have to pay all over again + more for the 5s.
Another consideration - when I got the 5's it was a sweetheart deal my Trans builder / HP parts guy put together for me that included: delivery, 4" down tube, turbo, sticks - he'd kill me if I told anyone the price, so it was a good deal but not cheap.