I use the adjustable 25 watt Hydor Theos in all my tanks, I haven't had a problem. Sounds like a good plan! I use timers on all my aquarium lights, they're only about $3 at the hardware store, and it's nice never having to worry about turning them on and off when I want to stay out late or leave town for a couple of days.
You should really take some time to research the Nitrogen cycle and invest in a good liquid test kit like this one: http://www.fosterandsmithaquatics.com/product/prod_display.cfm?pcatid=4454
recommend doing all your supply shopping online. Pet stores mark up each item about $10 or more in order to recoup the losses they incur by having to pay for maintenance, utilities, the mortgage on their stores, employees, etc. Online stores don't have to worry about many of these costs and pass the savings on to you. If you order multiple items, you'll end up saving a ton, even with shipping factored in. Things like gravel, silk plants, heaters, gravel vacuums, test kits, dechlorinators, decorations are great items that you can save a lot of money on if you buy online. If you live in the United States, I prefer to do my shopping here: http://www.fosterandsmithaquatics.co...lies/pr/c/3578
If you're Canadian, you should give this shop a shot: http://www.bigalsonline.com/