No experience specifically in clothing but IME the above mentioned countries are extremely eager, competitive and on the whole, can be totally trusted. They are more likely not to trust you I would say and will almost certainly want payment in advance after a sample has been provided. It's usually better to visit and meet people in situations like this but I guess for 2500 pieces, it's maybe not worth it in your case.
I wouldn't bother with an agent.
Keep googling and contacting - there should be plenty of takers even for small volumes.