The tank will be fine
If you use a HOB filter, I would suggest an Aquaclear or similar type that does not use throw away type cartridges, and has a good sized box which allows you to use your own choice of media (such as floss) for bacterial filtering, or carbon after medication treatments.
I, personally, wouldn't use the light, at least not at first, as the fish will be less stressed in an unlit tank. Once they are ready to transfer to their permanent home, you can use the light to acclimate them to brighter conditions for a few days, and then transfer them.
For Corys, I would gradually raise the temperature in the qt tank over a few days time to around 82 or 83 degrees, as the higher temperature will speed up the life cycle of the ICK parasite, making it easier to kill out. ICK is quite common with new fish of all types and there's a pretty good chance your new fish will have it, whether you see it or not.
Plastic plants, rocks, or other decorations are a good idea, as they give the fish someplace to hide if they get scared, therefore reducing stress. You don't need a lot, 2 or 3 fair sized items are sufficient.
I would definitely keep the bottom bare, or at the very most, no more than a 1/4" layer of gravel, since it tends to absorb medications, and will need to be throw out after treatment. The bare bottom is also much easier to clean, as you can see everything on the bare glass clearly. I suggest you clean the bottom of the tank with a small siphon, or even just some small tubing, after every feeding, and replace the siphoned off water with new, treated water of the same temperature. This way, you are performing small, frequent water changes, which is less stressful than a large one. Of course, you still may need to do a large change at times, depending on circumstances.
Corys are known to sometimes carry parasites which can be especially harmful to Angels and Discus, but I'm not an expert on other types of fish, so I don't know about them. Anyway, it's a good idea (in my opinion) to prophylactically treat all new fish for internal and external parasites, as well as bacterial and fungal diseases. There are those who will disagree with me on this matter, of course, but it works well for me. You can use any good medication designed for coverage of a variety of internal and external parasites, as well as for bacterial infections. Actually, that would be 2 or 3 medications. Treat for obvious problems first, of course. I won't suggest any particular medications, as there are a number of good ones available from your pet store or online. Most all of them will do a good job when used correctly, so follow the directions to the letter. Also, there is some really good information on treating fish disease on the web. Just Google 'fish disease treatment' and do your homework. It's boring, but the knowledge you gain is valuable.
The foam prefilter on your intake can take a week or two to become fully populated. I suggest you float a new foam in an established tank (if you have one) for a few days to a week, then you will have one ready to go when you need it. If you don't have an established tank, purchase a bottle of Seachem Stability, it's available online, and in better tropical fish stores, and add it to the quarantine tank just before adding the fish. Be sure to follow the directions. You will need to add it daily for several days. It is the only bacterial starter I've found that actually works (when used correctly). Most of the others on the market don't work well at all, in my experience.
I hope this information helps you out, if you have more questions, I'll try to answer them if I can.
Oh, while I'm thinking about it, check out this site: www.americanaquariumproducts.com
Carl Strohmeyer of American Aquarium has written some really informative articles on all aspects of freshwater fish keeping, including fish disease and treatment. He knows what he's talking about, and he tells it like it is. He's one of only a few who has actually done a lot of experiments in order to separate fact from conjecture. He won't steer you wrong.