Speaker questions:2 or 3-ways?

I have 2 ways in the front and 3 ways in the rear of my 89 firebird. I really want more and less treble and I think (if I am right) that disconnecting the rear crossover and tweeters and just use the 6x9" speaker back there that I will get a better sound. Any opinions on this? It seems like I should just use the rear for bass (use a low pass filter on them) and use the front for treble then mid goes through both.

ttt

So you just want to have an LP filter on the rear 6x9's and a HP on the fronts?..... are they running off an amp that has an built in LP or HP filter? No amp? You will need an inductor to lp a pair of speakers and a small cap for the fronts.

My deck doesn;t have a good EQ unfortunately and I can't control each speaker separately. I know how to do the wiring, I just was more curious about how it will sound. I actually went out and cut the tweeter and midrange woofer with excellent results. More bass!