That's great that you both are doing your research before you get a RES
There's a few things:
First - be aware that the 30 gallon will only last about a year if you're getting a hatchling. If you're getting a 4" turtle, a 30 gallon tank will already be a bit tight. It's best if you can go the largest tank you can right to start off, that way you don't have to do costly upgrades in the future.
The Repto Basking spotlight is somewhat unnecessary. What you do need is a UVB light and a source of heat. Most people use compact fluorescent UVB lights, since they fit in a regular light socket. There are also strip fluorescents. You'll want to get a bulb rated for 5.0-7.0 uvb. The 10.0 UVBs can be too strong, although if it's far enough away they're fine. The Basking spotlight can be used for heat, but a cheaper alternative is a regular incandescent household bulb. A 60-75 watt bulb usually gets the right basking temp.
The Aquaclear 50 should be adequate for a 30 gallon tank, although more filtration is always better.
One important thing that's missing from your list is a thermometer. It's important to know both the water temperature and basking temperature. Lots of people use digital thermometers that have a probe you can stick in the water. The kind that stick on the side of the tank are good for a quick temp reference, but tend to be inaccurate. You'll want to stay away from the glass type that stays in the tank, since it's possible for the turtle to break these.
I can't think of anything else at the moment. If you have any other questions, don't hesitate to ask
