I'm helping a friend with his setup and he'd like to add a 2-ch preamp into his HT setup. He has a Marantz AV7005 and a Threshold S/500 + Parasound 2205. He'd like to be able to add a preamp but there are only a few models with HT Pass Thru. Is there any kind of a standalone device that could be installed between his Marantz/Pre-amp to the Threshold? So he could select which preamp is supplying the input to the amp? Seems like there would be a market for such a device.