What type of I/O does the sub have?
If your receiver has preamp outs, you should be able to attach a sub with a right and left line level input with no problems.
Likewise, many subs have left and right speaker level inputs as well. These also can be used with your receiver.
Ss for connecting the sub directly to your DVD player, some do if they have analog outputs. Check your manual for this but understand that it still won't have the control options you would otherwise realize from the other methods mentioned. ...such as volume that tracks the rest of your system.