Technically, you need 8 including a sub, not 7, but the reality is, you can do a very decent system with just 6 - 5 speakers and a sub.
If you want boom, allocate the funds for the SVS sub right now

You will DEFINTELY not be lacking in the bass department.
For the rest of the gear, you could get away with just a receiver and good DVD player.
What's the budget??