1. Try Aquaforest Aquarium, they are in california, but i'm not sure if they're in LA. But you can order from them online, and their prices are just as cheap as you can find anywhere, and shipping wont be that much since you both are in CA. I was going to place my order with them, but used ADG since they are in Houston and the shipping ended up being cheaper.

2. I think either substrate would work for the emmersed method, but aquasoil probably would work the best.

3. Yes, aquasoil will leach ammonia for the first few weeks, but this doesn't harm the plants. It's bad for the fish, though. You can use zeolite in the filter, as well as mulm from an established tank, or an established filter. Plants will use the ammonia directly and help them grow. Also doing frequent waterchanges will necessary if you fill the tank right away. If you use the aquasoil with the emmersed method, by the time you fill the tank, the aquasoil will have cycled, the ammonia will have stopped leaching, and you will have a good bacterial colony established in the substrate, so you wont have to worry about many of the initial startup problems associated with the aquasoil. Still, waterchanges and some zeocarb in the filter would be a good idea to control the dissolved organics that might still remain.

4. 2 - 9L bags of aquasoil will be fine for your tank. I have a 29gal tank that is 30 inches long and 12 inches wide and I bought 3 9L bags, just in case. But I only had room to barely squeeze 2 full bags in the tank and it gave me about 3-4" of coverage. 2 bags were plenty and my 3rd bag is just sitting there "as a backup". If you want hills, or some extra just in case, you could maybe order an extra 4L bag, or maybe a 4L bag of the "powder" type. I figured that as long as I was paying for shipping already, it would be good to have an extra bag, for other tanks, or to replace some in the main tank if the need arises, or for whatever. I like having the extra around, even though I might never use it. :-)

Good luck with the new tank! Have fun!

-Mike B-