A word of warning: plecs, even small ones, make a LOT of mess. I would not keep more than 2 bristlenoses in a tank your size, in fact I think I'd make do with either one bristlie or the one candy plec. Particularly if you are keeping sensitive fish like dwarf gouramis or neons/cardinals. Another consideration is that corys need a clean substrate. I am currently keeping a 4 inch bristlenose with 3 corys and a single small platy in a 19 gallon tank with double filtration, and I'm having to do twice weekly gravel vacs to keep the substrate decent for the corys.
So in your case what I would do is:
either a trio of dwarf gouramis or a single male (they don't get lonely)- introducing these after the tank has been up and running for several months
a single bristlenose or a candy plec (note: you will probably get to see more of the bristlie- the bristlie can go in once the tank is cycled
5 peppered corys- can go in once the tank is cycled
6 cardinals