You use plain RCA type cables, from the right and left front preamp outputs of your receiver, to the inputs of the power amps. The power amps are hooked up to the front two speakers. The front right and left speaker connectors on the receiver are not used. You can confirm this by reading the manual for your Pioneer.
Most likely, the preamp will not be useful in conjunction with the Pioneer. If the preamp has MM phono inputs and you use a MM cartridge playing records, then you could use it for that, but otherwise, it is not a good idea to try to use it with the receiver. Basically, a receiver is a tuner (radio), preamp, and power amp, all in one box. You are planning on bypassing the power amp section for the front right and left speakers, hence the use of the Aragon power amps, but you are not bypassing the preamp section of the Pioneer, so you really do not need another preamp hooked up to it.
Now, if later on you want to have two systems, one with that preamp, and another with the Pioneer, then you would want to keep the preamp for that future use. But with the one system, it is not likely of any benefit at all.
