No, not unless you want your sub to run in highpass or your 6x9's to run in lowpass, actually there is a way to do it with active or passive crossovers i think but i am not sure of how to do it. It would be easier to go and get a 4 channel amp to run your highs off the front and the bubs off of the rear channel.
if your 6x9's are running in low pass then they won't be making any noise, just pounding like a sub. Just run them off of your deck till you get another amp or a 4 channel.