Need a little help

Hello everyone. Somewhat new to this hobby and need a little advice. My current setup is a 2.1 channel setup consisting of a Pioneer sclx-904 av receiver that I'm using as a preamp, 2 identical Anthem power amps that are feeding a pair of B&W bookshelf speakers (they are biamped). My question is this; I recently acquired an Nad preamp. Can this NAD be integrated into my existing system somehow?  What would I be gaining? I read that an external preamp can be hooked up to an av receiver, how would I do that?? Also the NAD only has one set of preout's, and does not have a dedicated sub out, I still want to use both Anthem amps and my Klipsch subwoofer, but how do I achieve this with only one set of preouts( left/ right) on the NAD?? Any help is much appreciated. Thank you!