I would use the pass thru on the subs to the tops, that way you can adjust back the amount of bass on the SWA1801 and you have plenty of it. 1050W (combined 800+250) per side vs 60W for mids and 25W for highs. As to the PX you don't want to use it for a crossover but there are other features such as feedback control that would come in handy since your coming out of an analog mixer with none of that.