Whats the best way to run six speakers off a headunit which

Whats the best way to run six speakers off a headunit which has a four channel amp fitted ?
Basically I have subs and all that figured out, the new head unit pioneer DEH39000 is coming this week.
I have an '02 protege and it has six stock speaker places but only four speakers two front door and two rear deck . there are two open places in the rear door for 6.5"s which I have laying around. I wanted to know the best way to wire them.
By the way, the stock speakers already have great sound there 5x7 and 6x9 pioneers so I don't wanna mess anything up. I know they take 25 watts each.

Is it smart to run two more speakers off the head unit, or am I supposed to just get a cheap two or four channel amp to run the rear speakers?
And if I can run them off teh head unit, how could I wire them theres no speaker wire now in the rear door places ?

Thats what I planned on doing an amp for two of the speakers . but there's already speaker wire in the front and rear deck places so I thinked the simplest could be to run the amp to the new rear door speakers which can handle the most power anyway ..
any reccommendations on a real cheap amp with something like two channels 50 watts each?

Get a cheap four channel amp and run all six off of it. Run the front door speakers off the front channels on the amp. Then, run all four rear speakers off of the rear channels on the amp. Just wire all four rear speakers on the same two rear spaker terminals on the amp in parallel, and this set up will blow away what your head unit can do, if you just get a 30x4 amp or so.

If you don't have to have six speakers, I could install the rear door speakers, run them off the amp, and scrap the deck speakers. This will sound real nice and clean. I hate how muddy speakers on rear decks sound, real good ones .

You will be surpised at how much better your stereo will sound with a separate amp, a cheap one. don't go crazy on the power of the amp if you're using the stock speakers, 30 or 40 watts per channel will be more than enough, if you upgrade your speakers down the road.

You suggested a two channel amp If you're going to amp anything, amp the fronts 1st.

I could wire the four rear est [, speakers off of the headunit. Now, purchase a little about 50watts RMS x two @ 4ohm amp for the front speakers.
This way you may be able to hear it deafening and clear up front which is really all that matters for the driver/fr passenger and the rear passengers will not have to cover their ears because it is too deafening.

Have Fun.