The place I got my seeds from, highly and i mean HIGHLY recommends either Promix, OR a almost identical product I found at home depot called BM1.
Feel free to check out my grow for the BM1 info, I actually had 2 soils to start and one plant was doing so much better (BM1 soil) that I transplanted my other plant into it as well. After that I've had 2 nice healthy plants !!
Last I checked here in Canada (toronto atleast) they sell all sorts of types of promix at Lowes.
Hope thats a minor help,
-Tdot