Metal conduit is often a conductor of noise and electrical signals. You should not be using conduit that is metal unless it is properly grounded to remove interference. In almost all situations, it is not necessary to have any conduit in place at all if you pay attention to your wire runs. Try to run the speaker wires away from power wires and cross at a 90 degree angle if possible. Your speaker wire gauge should be excellent for things it seems like. The main reason to run conduit is not to protect from EMF but to allow for wires to be retrofit into place if necessary. For speaker wires, this is almost never the case, but I often will pull 14/4 wiring instead of 14/2 wiring so that I have spare conductors available to allow for doubling up if I want or to bi-amp if I want. There certainly is a minimal cost impact to do such.
Keep in mind any OTHER areas you may even possibly want wiring and speakers run at this time. Before a basement is sealed up you can get speakers to many locations that you won't ever have access to again. Outside, different basement spaces, even the main floor. You should also consider your equipment location and think abut whether it truly meets your needs for what you are trying to achieve. I rarely recommend theater gear go into a theater, but try to find a better spot to hide the gear and give room for it to make noise and breathe as it needs to, preferably in an unfinished space... which complicates wiring a fair bit.
I would not personally go with conduit to speaker locations, but I would loop wiring in a manner that allows versatility for speaker placement... on-wall, in-wall, towers, etc.
Don't forget, your subwoofer will need a power outlet right next to it and it may be worthwhile to run for a couple of subwoofer locations.
