Khoi, I do not mean to belabor the point more, but from what I read in the little research I did about the mechanical Pentair modules was that they required changing a lot, especially if there was a lot of mechanical filtration. Now these were cichlid tanks which get quite messy, but still.
I know someone mentioned it, but you might want to also take a look at
Reefs.org's pump selection guide and their
head loss calculator. This will give you a good idea of what you will be losing as you pass the water through all those modules. If you have not heard this enough, I would go for two pumps, just in case.
I think all this advice is being thrown at you because we are all SO jealous. For your stand, is it built already, or are you going to build it yourself? Thanks again for putting up with us and sharing this!