I have had my Rio 125 set up for the last two months using seachem fluorite as the substrate and I am using the tubes (2) that came with it the only modification was to fit a Juwel reflector for the front tube. So far all the plants are doing pretty well. I have
vallisneria spirallis-has doubled in size and is putting out runners.
Hygrophila polysperma - I have had to trim back as it reached the surface
Echinodurus Paniculatus- slow to start but are now putting out new leaves
Cryptocoryne wendtii- another slow grower but now putting out new leaves
Java fern- several new leaves.
Echinodorus tenellus- lots of new plants forming on runners
I would suggest that if you are going to use plants that are happy in low to moderate light then the standard tubes are ok and a good substrate is almost as important.
Cheers Businesslamb