hey caged great
what kind of wall would be the strongest?? i would guess and engineered concrete wall. back in the day that i did construction we did a massive concrete retaining wall in kamloops. the footings were about 25' wide and the wall was thick enough that you could actually walk inside the wall before the concrete was poured!
what company - sorry. no clue - i live in kelowna
if you want to "do it yourself" you could always do a block wall - they aren't that difficult and you can save yourself a ton of $$.
this is what my dad and i did a few years back when my wife and i built our place:
http://forum.calgarypuck.com/showpos...4&postcount=12