that seems to be quite a few fish for a 10 gallon. A little too much if you ask me.
I would not get the Aqua Clear 500 for your tank becuase it will be WAY too strong and just blow your plants around like crazy. Try an AC mini or something.
The Eco-complete is very good and you will get approx 3inch of substrate with 20 lbs.
I would not add the sand, as Eco-complete is a complete substrate and works well by itself. Anyways if you add sand it will just go to the bottom of the substrate.
For the lighting, flourscent light have a determind wattage for a specific size. Meaning that you will only be able to use a 15watt bulb in an 18" strip. You could op for a dual strip, a PC retrofit kit, or ODing your light (you can find many good article here about ODing lights)