You and I are in quite a similar situation, I have an almost 3 and 1/2 year old daughter, and a 13 month old son, I too thought I would be done at 2, but after having my son, I still feel incomplete in a way. I talked to my DH about it, and we agreed on one more. We don't necessarily have financial issues, but we are looking to renovate our home soon, which will cost a lot and we will need to cut many expenses here and there.
Since I have 2 now, I can say with confidence that we already own all the big ticket items, such as a crib, mattress, dresser, swing, high chair, pack and play, ect. We actually have almost everything that we wouldn't need to buy anything else for baby #3 unless it were another girl, I gave most of my daughters baby clothes away, but in comparison to other items babies need, clothing hardly costs much. I anticipate the 3rd baby will probably have the least amount of expenses out of them all since I've held onto everything. Do you still have everything from your sons?
To be honest, since I had DD first, I of course bought very girly items and feminine printed stuff, a purple bumbo, pink bibs, and flower printed high chair for example, we didn't have enough money to replace some of these items when we found out we were having a boy, so DS has sat in a flower printed high chair, used a pink bib, pink towels, and sat in a purple bumbo
not that it makes a difference to him, if anything I was the only one initially bothered by it, now I really don't care, as long as he has a place to eat, and food still tastes the same to him. If I had another boy I'd probably do the same again.
We are TTC around early 2016, if you figure it out and set a date close to mine let me know, maybe we could be WTT buddies, then TTC buddies