I was thinking of doing 1 big canister, but decided on the two canister approach in order to increase the number of flow angles and to split up the plumbing of inline equipment to get the most flow out of each filter instead of bogging down one filter with a few inline attachments.
Lily pipes look great, but too expensive for me. Paying $400 shipped for the 75P is already a huge purchase, so the addition of lily pipes is just too much for me. Also, cleaning them and the fragile nature are discouraging. However, the main reason is price.
The light stand will be DIY, so it can be as high as I need it to be (of course only up to the ceiling). A pendant would be nice, but from what I've seen, MH pendants only go down to 150W, which would give me almost 4WPG. I'd rather keep the lighting to about 2-3WPG to slow growth and decrease maintenance. That's why I'm looking more into the T5 fixtures.