Consider a reasonably good Phono Preamp like the Audio By Van Alstine Vision (Absolute Sound Product of the Year Award) $499.00 or a Black Cube SE (on the used market). Experiment with your existing components and utilize what ever configuration sounds best. I would go two channel for your analogue front end and try to eliminate any type of switch to select speakers. There's all sorts of options; if the NAD has a phonostage (that is suitable for use with your cartridge), you can use that and utilize different pre amp / amp /integrated configurations with the equipment you have, until you come up with the best sounding.
Good luck
Good luck