Folks around here keep discus in hard tap water with a pH of 8.2 with no problem. For breeding you would need to make it softer and more acidic, though. There are some discus website where you could probably find more info.
i've seen pretty good discus raised in water ph 8.4, gh 25 and kh 18. water was softened to get decent hatches, but the fish raised in that water were fine in it.
i find however that even though fish can be kept in these high ranges, their colours will improve in softer water. but, making soft water is an art, not to be practiced with good discus. get good with some rams, then try growing out larger s/a fish. discus will not do well with their water parms going all over the place.