sorry for the delayed response here, have been extremely busy, but did see your post yesterday evening before i went to bed, just a bit of information on discus, they are not the easiest fish to keep, they are extremely sensitive to ph changes, very picky on their ph 6.4 to 6.7 is their range you need to make sure you keep your tank at that range and it stays steady if the ph spikes for any reason you will lose the fish with out immediate remedy, although they are like many fish and can and will adapt to higher ph levels, although they will never reach their full color potential if kept at a higher ph level as over time even though they get use to it, it's still an added stress on them. they need a protein based diet, i feed mine blood worms and brine shrimp that have been raised on spirulina so that the fish get a bit of crude plant matter it seems to keep them happy and they will eat right from my hands at this point, my big blue diamond will come up to the top of the tank and rest against my hand as far as tank mates, you need to keep docile fish that don't dart around very fast as these types of fish can stress out the discus, neon, cardinal tetras, black neons, dwarf ram cichlids, cory cats, and angels are commonly kept with discus, although i would be careful with the angel fish, come feeding time or even if you have a pair of angels and they breed, they will get super aggressive towards all other fish and can cause harm to the discus. shrimp and live plants are a great mixture for the discus as well, buy ghost shrimp as they are cheap, and make a great live snack for the discus. you could also put in fresh water clams , fresh water flounder, and i have found that dwarf puffers, (aka. pea puffers) make great tank mates as well. plants i would suggest are lilies, swords, anubias, spiral crypts, dwarf onion plants, foxtail, cobamba, money wort, and other warm water plants. discus need to be kept at a constant temp of between 84-87 degrees in that range they will be more than happy, if they are to breed you need around 88-89 degrees. you have to consider where they come from in the wild. anyone else who may see something that i missed may be able to help out as well. i would suggest buying a book on discus keeping and breeding. this will help you make your decision.
As far as the are they hard to maintain, well that's really a point of view question, in my eyes i don't see them as hard to keep, however i do invest a lot of time and money in my tank, on the other hand it's what makes me happy and keeps me sane and stabilized in this crazy hectic world. you can actually keep three discus in your tank and maybe a fourth if you get them when they are small and all the same size they will grow together and adapt to the tank just fine, just remember the more fish you have the more bio load you will end up with so over filtrate and when i say over filtrate i mean it, don't skimp on your filtration and you should do just fine. if you look at my profile you will see that i am probably overstocked in my tank but have been for months on end now and haven't had really any problems other than the angel fish that had a disease and well passed on to the other side so to speak. when buying your discus make sure they are all healthy, active and show no signs of stress, you will know because the colors will be muted and their slime coat will look sort of milky, it's the first indication there is something wrong with the fish and or the tank.
Hope some of this helps and i hope it doesn't scare you away from keeping discus they truly are amazing fish and will keep you watching for hours on end.