Great advice and good point Dave. I was under the impression that he was aiming more for a tank similar to mine because in his first post he mentioned he was looking into starting a tank for a few discuss. Mine is definitely focused on the fish over the plants.
I'd think about what types of plants you want to keep, what the scaping will look like, etc. I really wish my tank was wider, as it adds much more room for scaping.
My tank has a lot of plants in a lot of varieties, but most are native to amazon type waters. Not only are they somewhat "easy" plants to maintain, but having the right conditions helps them flourish. I was at a farmers market the other day, and a friend asked why nobody had bananas. The farmers response was that he had tried growing them, but they would only get about an inch long. This is what I was aiming for when I set this tank up, having a biotope as close to natural, (I consider mine an Amazon bio), as I could while trying to use as few chemicals as possible.
I did run co2 on mine for a period, but I must mention that I ran the co2 through an Eheim canister filter, (earlier I said I had never used a canister, but I meant as a main source of filtration), to be chopped and pushed directly into the water column near the bottom. After awhile I started to wonder if it wasn't necessary. So, I cut it off gradually and saw no difference. It was nice in the beginning though. There is also a lot of discussion as to whether co2 should be shut off at night due to ph swings.
I agree with Dave on fertilizers as well. I use them, just not a whole lot. Mainly when I do a lot of trimming or after water-changes. Another member here, PEMfish, has a good deal of experience with planted tanks. He prefers dry fertilizers, while I prefer liquids, specifically Seachem brands. It boils down to what you like and what works the best for you.
If you intend to keep plants for the aesthetics in addition to comfort value added to your fish, I recommend going with a wet/dry pouring into a large sump. If plants are more important, like Dave says go with a canister, but get a high quality one. My reduced water changes doesn't mean lower quality water parameters, it means the water is running at what discus prefer and makes them healthy. The guy I bought mine from won't sell you his fish if your ph is over 6.5. He is the one I mentioned who gave me a much better insight into keeping discus, with decades of insight, knowledge, and trial and error.
The benefits I find in running a wet/dry and sump is I can keep it raised vertically pouring into a rather large sump. The benefits are less top offs, although this is arguable, since I believe the evaporation rate is higher. Larger volumes of water are more stable, my sump adds somewhere between 15-25 gallons to my system if not more. The pure over-kill with the size of my wet/dry allows massive amounts of biological and mechanical filtration. Finally, it allows a place for more things that don't have to be in the dt, such as heaters, big bags of peat moss, uv filters, and anything else you may want to hide, (too bad skimmers don't work in freshwater).
To sum it up, I'm only offering what has worked the best for me, I've kept discus for about 9 years now. This is mainly a sw sight, but there is a freshwater section here. I think you will find a lot of insight and great advice from Davek, PEMfish, and Grendelprime as well. All have kept planted tanks, and most have kept discus.
Didn't mean to write a book, I apologize. Once again, good luck.
