Once you do decide on a brand make sure not to stock up to much, just in case your LO has some sort of sensitivity to it and you have to switch brands, I don't think stores will take formula back once it's been bought and I'd hate to waste the money!
Not sure if they have this in the States, but here in Canada you can get samples from a lot of the different companies, we did that and than chose which one we thought suited us best and went from there. Luckily Hannah never did have a problem with what we chose so we kept on with it
Also we just happened to chose one that had added Omega 3 & 6 (not all do), several months down the line after reading about the huge benefits of those added supplements I was really happy we'd gone with one that had it