that kinda sucks, so i guess with discus i can only really get petco style fish not too much else. I was told you should keep discus in groups of 4 or more, if not they get too territorial
There are things I want to say about this post, but I'll bite my tongue and keep them to myself.
Yes, discus really do need a MINIMUM of 4-5, preferably 6+ to be happy. If you're interested in some of the trials and tribulations I went through getting my 55g tank converted to discus, check out this thread.
http://www.aquariacentral.com/forums/showthread.php?t=134578
As I believe was mentioned by another poster in this thread, you are in for a LOT of water changes. You're looking at an absolute minimum of 2 50% changes a week... and keep in mind, I really do mean MINIMUM. I do 50% changes every other day, and more often than not will do a ~30% change in between the bigger changes. On weekends, I'll substitute ~70% rather than 50%. (keep in mind, I do go a little overboard with my tank, as I like to keep the water as pristine as I can legitimately keep up with... most discus breeders do 80-100% daily water changes. To be honest, the 80g tank you mentioned would be better for the discus than the corner tank... I keep mine in a 55g tank as it is the largest tank I can keep presently. (and yes, by looking at my stocking list, my tank is a bit overstocked. I won't make excuses. Suffice it to say, I plan to sell one or two discus, and then consider it pretty much stocked, though I could likely keep all 7 and have them be happy/healthy, granted the immaculate care they receive)
One last thing to consider: diet. Discus will not thrive nor survive on tetra-min flakes. They need a very meaty diet, supplemented with some vegetation. I feed my discus blood worms, beef heart, plankton, brine shrimp, flakes, hikari algae wafers, HBH super soft carnivorous and herbivorous pellets, and on rare occasion, hikari gold cichlid pellets. (less than .5% of their diet)
Good luck, and keep us posted.