Help me decide...What should I buy (Red-Eyed Leaf Frog's)??

I have 2 Red-Eyed Leaf Frog's. I want a good combo to maybe some day try to breed them. I know one for a fact is a male...he calls everyday. The other I thought for sure I heard him calling when I first got them, but I could be wrong. So, should I:

Go back to the store where I got these two and get two more (sub-adults) for $35ea. and hope I get a good combo?

or

Go to another pet store that I know has only one adult Red-Eyed Leaf Frog left and assures me he's 99% sure it's a female for $50?

Also, I think I've reached my max in frogs for my 34 gallon tank, right? Or am I overcrowding it?

Thanks!