Get the surrounds first so that you can enjoy HT, SACD, DVD-A, DTS music. There are more sounds effects with surrounds than bass, not unless you watch a lot of action movies. Even if you watch action movies, bass note doesn't play all the time.

bottom line, you get more bang for buck with surrounds, but you will NEED a sub at some point. When that comes, you will FEEL the movie instead of HEARING it.