The best lights for seedlings are fluorescents. You don't even have to use expensive ones, I've seen plants on these forums which were grown with those compact fluorescents and they look good. The best thing about them is that they don't produce much heat, hardly any at all so you can place them within inches of the young plants. I think 400w would be a bit much for tiny seedlings. I've never heard of many people start seeds off under a 400w. Because only small pots are normally used to start seeds, the heat from a 400w would dry the soil out too quickly I think, so you'd have to keep checking them constantly. As for soil, there are several quality soil mixes on the market. There are those organic "super-mixes" which the hydroponic stores sell or you could use a basic, multi-purpose compost like I do; it works well.
For seedlings and clones I use a fluorescent unit called 'light-wing'. It takes 2 x 55w tubes and it works great. It makes topping the plants a bit awkward because the nodes are so close together.