I would definitely stay away from the dwarfs as Vinnie said as they are too difficult to feed in a large tank and are usually wild caught. The biggest thing you want to be sure of is that you are buying captive bred seahorses. That is why Ocean Rider has been recommended is because they are tank bred and not raised in a netted off area in the ocean. The main reason for wanting tank raised is because they will already be eating frozen food, most likely mysis shrimp, when you buy them. If you go to an LFS to get them you need to watch them actually eat the frozen food before you buy them.
One of the best things you can do before getting them is what you are doing now and that is research them. You can find out some very good information on Seahorse.org as well.
I wish you the best of luck.