I couldnt agree more, people that keep discus know about discus, people able to BREED them really care about about discus so its always better to get them from a breeder for cost and also because you know they are well looked after. Make sure you find out what water stats the breeder has regarding pH etc and more importantly temerature etc.
With most discus being tank bred now they arent as hard to keep as they used to be but its best to be safe than sorry, my local papers, admag etc are always full of breeding pairs of discus about half the price you pay for one in the shop. One bit of advice though if you buy privately pick them up from the seller, make sure they are swimminmg in the tank when you arrive so you can see them in their enviroment.
Truely the KINGS of tropical fish....good luck