Hmm. I guess you already knew that the smaller the tank is, the less margin of errors you have. I would go with a 32w pc and if you change water more rapidly than usual tanks and check your water every now and then, you should be alright. If you have other tanks, you may want to transfer water from your older tank(s) into the 5. If you do that, you don't have to wait for the cycle to complete. As for other equipments, I would go for a small hang-on filter with a bio-wheel. Arggghhh, I can't really think right now. HTH
Oh, as for some suggestions for fishy. The only small fish I can think of is a clown goby. A lot of personalities and they stay very small, but I am not sure if a 5 can handle its bioload.