I don't DOUBT that you probably are making more than enough $$$ to cover two kids. Money is the least of the problems with kids, though. And believe me, if anyone understands about wanting to have another child, it's me. But as a responsible adult you have to weigh the dream of what YOU want versus what is truly BEST for the child you have responsibility for now. Siblings do not always get along, in fact sometimes they're positively homicidal to each other. And I'm telling you, boys, in particular, don't get easier. I'm not exaggerating, boys go through a ... stage ... is all I can think it's best called. They turn into total fucking assholes to the adult women in their lives, particularly if they live in a single parent household (personally, I think it's genetic to head off inbreeding), but the teen years are the worst, second only to the headaches of dealing with daycare and elementary school situations.
$$$ are the least of the problems being a parent in general. Fuck dying, what happens if you get in a car accident and can't move for about a month? It's a shit load easier to farm out ONE kid, scrambling to get coverage for two is twice as hard.