oh, i dont think so, i would get the 6 cardianals and the 3 corys, a pretty good stocking idea i think. I personally wouldnt get the guppy becouse i cant stand having a tank with fish from different origins, lol its just me.
my 2 cents
Six Cardinals and three Panda Cories would be okay. But if you decide to get one less fish just to be on the safe side, cut down the Cardinals to five, don't cut down the Cories because they should be kept in groups.
Cardinals produce almost no waste and neither do cories. Your tank will be just fine with that stocking and I will even go out there and say ya cut back on one cardinal and you would be ok with 2 guppys.