<font color='#000000'>Speakers need an amplifier to drive them. A DVD player doesn't usually have an amp. The systems you saw, commonly called "Home Theater in a Box" (HTIB) most likely had an amp and DVD integrated on one chassis -- but it's unlikely that your DVD player purchased by itself does. The only kind of sub you could run directly from the DVD player would be a "powered" sub, which has an amp built-in. I do not know of a powered sub with outputs for main speakers, however. The connectors you saw were probably inputs. The built in amp usually just powers the sub. So you still need to power your main speakers.
If you just have two main speakers (no center channel or rear surrounds) you could look for an integrated stereo amp for the main speakers. Otherwise, you'll have to bite the bullet & get a reciever. Actually, a reciever might be cheaper! Integrated amps are part way down the road to separates and aimed at audiophiles, and thus tend to be more expensive.
One possible cheap solution: Radio Shack has a simple, cheap integrated stereo amp for about $60. I think it's 30 watts per channel or something.</font>