I found a way for you to upgrade your lighting cheap if you want to, you'd need a glass top or something though. I was at a hydroponics shop today and picked up a sunblaster 24"T5HO fixture/lamp for $30. It's a 24 watt bulb and linkable, it also seems to give light all the way down to the substrate. I'd expect it to be cheaper as you live in the states, maybe $20-$25 for the fixture. 2 of these should be able to get you into a medium light category without breaking the bank on an expensive fixture. Other than that sounds like a decent plan, lots of plants are good. And yeah you could probably even go with a larger school of like 20 total, but I'd say stick with a smaller number, and if you stay with smaller ones get a nice colony of shrimp going.