Passive/line stage HT preamp?

OK, so I'm upgrading my HT. I'm getting the Oppo BDP-105, an HT preamp, and a projector (likely Epson).

My question is this: Is there such a thing as a passive, or straight line stage, home theater preamp? Can't I just let the Oppo handle all the processing? Room correction aside, are there codecs/modes that the DVD player can't handle?

Thanks!