You could go planted with a 10 gallon. You can get some Java Ferns, mosses and a crypt or two (depending on the variety they can get bushy)
I love corys also they are fun and fascinating. I think you could have 4-5 of them and a small school of neon tetra or rummynose tetra....most tetras stay small which will really help in your case.
With low light plants (and your standard hood light) you should be able to keep most low light plants without any special substrate just regular gravel and some root tabs for the crypt plants or vals.
Check out the planted tank section for more info on plants for your set up.
I have personally gotten plants from many members here in the barter/trade section which is always a good way to go for quality inexpensive plants....there is also a seller online (started on ebay) called mikeswetpets.com who has great plants and at a good price and he will replace anything that doesn't survive in shipping only happened with me once but he was great about replacing.....you can also check out aquabid.com
Good luck, sounds like a fun tank.
