Are all the juvi bristlenoses staying? I think that's where you'd fall down...if you're only keeping one or two, then I think you could up the cory numbers and the harlequins numbers, if you're keeping all of them, then I'd leave the harlequins as they are and up the cories to 6.
What about something like midnight emperor tetras. Black with blue eyes. Very striking in a shoal. Didn't you have cardinals in here before? I can't remember!
Was considering Purple Emperor's? Maybe 4-6? That would keep the stocking down too as i believe they don't need to be in a massive shoal as they're not particularly good at schooling anyway?!