I had 6 males for my own 10 at first, but we wound up taking back one of the boys around day... 12-13 because of harassment :( If we didn't have Honey, the mystery snail, and Bowser the betta, we'd prolly get more guppies (or I would anyway).
I'd leave it at just the guppies, maybe two otos. More than 8 guppies is pushing it, imho. You could prolly do about 4 kuhli loaches, though. I've heard they've got a really low bioload. If you do look into them, they really need to be in groups, I bought a pair and I really feel I should have done 3 minimum, want to get another 2 at least in the future.
Just keep in mind that guppies are top-level swimmers. You should look into bottom-dwellers. If not loaches, then the mini/pygmy cories. At least 3 of them as well.