The trade pipe idea is good but may be tuff to find a match member to trade with. Keep looking though.
Everyone is pleased with the 5 or 5b and I am sure you would be to ryan. There is a fun factor with the 9 and brother mx that has more hit and more rider input and work required then the 5 and 7. Depends on your riding style and what you enjoy vs what your lap times would be the last 2 laps. Your body will tire more quickly with the 9 and mx vs the 5 and 7. You can see this pipe personality connection between these pipe options by looking at the rear cone area and also possibly compare a little bit to other pipes personality by doing the same. I have loved my 5 but for a duner may go 9 next time like tony did for the fun factor and a little more RIDING required.