First off here is a link to the manual for your amp, open it up and print it out since it has most of the answers you are looking for: http://www.teamclarion.com/sharedwebdbs/clarionsupport.nsf/b519d112bdcca8b588256a630071fab1/e469e62058003a2f88256e43006d52b3/
The easiest way is to wire 1 speaker to each channel of the amp as shown on page 4, I think this is how you have them now. SWITCH THE REAR CHANNEL INPUT SELECTOR TO 2 CHANNEL INPUT. Set both front and rear channel crossovers to high pass and adjust the frequency to about 100hz so the amp can push the most out of your speakers without distorting from bass overload. This should let your basslink do it's job. Fine tune the gains and crossovers on your amp and basslink until it sounds good. Do it in the water not in a garage since it will sound completely different out in the open space.
Your RCAs should work fine the way they are.