Looks fine. I ran a single AC70 on mine for months, and it was just fine. Now it has an AC110, AC70, and a Hydro V sponge. ^^ I've seen a 55g that just had about 9 of those 10g-rated Internal filters, and when the water was tested, it was perfectly fine (Nirates were at 6ppm when water-change day came around)
But your setup looks perfectly fine, but if you want to upgrade, do it. Since, as always, more is better.