If you want a breeding pair, I'd go with 6 or so, this way you're almost guaranteed to wind up with at least one compatible pair.
What sized tank are they going in? For a breeding pair you'll need a massive aquarium. Even a lone male Jag should be housed in a tank with a footprint of no less than a 5' x 1.5' (roughly 100 gallons, depending on height). You'll probably also need a divider as males tend to beat up on their mate. At least this was my experience.
The Managuense is a beautiful fish; I'd recommend it if you had the tank space.