Your previous tanks look great. It looks like you're doing a good job of selecting "clean" looking equipment to look like ADA. Looks great!
What's the advantage to running the two filters in series? I've never seen that done.
Thks for your reply.
Running filters in series is a very common practice in Japan, started by Takashi Amano.
The idea is to have as much possible area for the bacteria to grow.
In japan, is very common to see a small tank with 16 liters of biological media on it.
So, first of all, the advantage to have 2 (or more) canister is: Maintenance. You can clean a filter per month and you still giving time for the bacteria to stabilize in the other canister.
Second of all, on a planted tank you want less water movement, so you don't mess with the plants co2 absorption, otherwise you could just put the 2 canisters running separately on the same tank (but 4 pipes inside a tank wouldn't loo too great on a ADA style tank).
Take a look at the link below, it´s from Eheim Japan...
If, like me, you don't understand anything at all (LOL), do a little google translating...
Hope it helps.