That is an enormous tank! Be aware that it's gonna be a pain in the ass to change that much water every week or two. I like the ten gallon size myself. If you're planning on eight plants, I'd set up two ten gallon tanks instead--having eight plants sharing the same reservoir is just asking for problems that you don't need for your first go-round. Eight plants will be constantly competing with eachother for light and space, and may have different responses to the shared res. I wouldn't go with more than five plants on your huge tank.
As for the air stones, you want one that diffuses the air into the smallest possible bubbles, but I couldn't tell you offhand what brand to look for. Most any stone should work, though. edit: I use the ones that look like sandstone. I'm not sure how well those plastic ones work.
The net pot size doesn't really matter, it's just a support for the plant. 95% of the roots will be outside anyway. I use 3.5 inch pots, I believe.