I think both are a good idea.
If you get something like the MXR Preamp you can use it to EQ your sound when you're going through your normal amp, like an active bass pre amp, then use the DI out as backup if your Orange head blew up mid gig or if you weren't using an amp like you mentioned above. Then if you did just rely on the FOH system you can still EQ the DI signal.
I'm also a big fan of using a compressor with a bass. Just helps keep everything level, especially when using fingers.