If you get the Crown, dont worry about blowing up the speakers. It has gain controls at the front. Most home use power amps do not have gain controls, except the high end ones. (yet another advantage of getting the Crown XLS 1502

). Yamaha wxc has analog out which you connect it to the Pioneers line in, whilst setting the Yamaha WCX 50 in player mode. (There is a button on the back to set it as a Preamp or Player as shown in the video). If you see noticiable improvement in the highs and mids, You might think of getting the power amp to add to the midrange sweetness and bass slam. Whilst connecting to the power amp, you need to switch the Yamaha from player mode to preamp mode. So for now, hold the power amp, get the yamaha and see how it performs. Look at the video again, it has those explanation.