One option is to build your own dump (overhead) filter - basically a DIY sump on top of the tank - and use one of the FX6s to pump water to it (just modify the output of the FX6 to go to the overhead filter instead of back to the tank). To make it so you very seldom if ever need to clean the FX6, put the input behind a Poret wall on one side of the tank... or put a pre-filter on the intake.
I used a set-up like this for many years on a 180g.
Otherwise (and if the tank's already drilled), I'd just DIY a sump under the tank.