well ... the sponge by itself won't accomplish much filtering, since it's just coarse enough to stop the powerhead from ingesting large pieces of debris ... not really designed to filter particles out of the water.
filter and pump combo sounds expensive, at least, more so than a small filstar, fluval or via aqua canister, and, IMHO
not well suited for filtering a paladium, at least, not as the primary / only filter.
filter is designed for biological filtration only ... you need to use fine mechanical filtration before the FBF
; fine mechanical means several layers of filter floss, or fine sponges.
Basiclly, water with no visible debris is what a FBF
filter needs, because it works on taking microscopic waste, ammonia and nitrites out of the water ... anything larger causes the sand to clump up and clog, rendering the filter useless.
Also, the filter only provides biological filtration ... if you're concerned about smell and the color of the water, you also need chemical filtration by means of activated carbon.
Rainbow Lifeguard makes some nice equipment, but it's overkill for what you need.
A $50 to $70 canister filter will work best, be easy to clean, and if you decide to ditch the turtle and go all fish, it will work well in a true aquarium as well.