1997 Grand Prix install questions

hi, all

i am currently attempting to upgrade my stereo in my 1997 grand prix SE.  I've upgraded my 5 1/4" speakers in the front doors successfully.  This weekend, though... i was installing some really nice Infinity Kappa 6x9's in the rear deck to replace the crappy stock Delco speakers, and i discovered something odd.  I have the 8 speaker premium system in my car (5 1/4 with tweeters in the front doors, 6x9s and 4 inch speakers in the rear deck).  It appears whoever owned the car before me may have attempted to alter the speaker wiring and really screwed it up.  After removing the deck panel to get at the speakers, i found that only the 4 inch speakers had the full sound range coming through them (trebele, bass, and mid-range) and the 6x9s only had bass sound coming out of it.  I hooked my new speakers up to the existing wiring and had the same problem.  So, i removed the 4 inch speakers and used those wires to connect to my new 6x9s, and completed the install.  While my new speakers sound excellent, if i go to replace the 4 inch speakers, then i'm only going to have bass coming out of them.

Does anyone know what the wiring issue (if it IS a wiring issue) might be? and how i might go about correcting it? My instinct tells me i might need a crossover or something, but i don't have a lot of experience with 8 speaker systems, so i'm not even sure where to begin with it.      Is there some piece of hardware that's supposed to be on these type of premium speaker setups that allow all sound ranges to be split between the extra speakers?

2nd question: my head unit is a Kenwood KDC-MP819 deck. nice deck, has most of the features i want in a stereo....EXCEPT for the fact that it has no decdicated RCA pre-outs for a subwoofer to be added to it.  It only has two sets (front and rear).  If i theoretically wanted to hook up a one or two channel amplifier in the trunk to power a couple of subs, could i use the rear pre-outs on the deck to hook it up? is there anything i should be concerned with doing it this way? will it even work?

thanks in advance....

sounds like you've probably got the Monsoon amp in there which is splitting signal to different speaker sources....you could bypass the amp and go direct to the speakers to eliminate this problem.....

you can use the rear pre out for a sub no problem but keep in mind that because it is not a non-fading pre out, if you fade to the front more you are taking signal away from the (rear) sub output......

does that monsoon amp come stock in my car? i didn't see it when i was in the trunk, but then again... i wasn't looking for it.  if i find it, i'll just disconnect and rip the sucker out.

as for the subwoofer issue, so, you're saying if i keep the fader equally balanced between the fron and rear, i should be ok, right? if i keep it balanced, will an equal amount of wattage go to my amp and rear speakers, or will i lose power to my speakers by hooking up an amp to those rear pre-outs? and if i get an amp with one of those knobs that installs near the dash that controls the sub level from the driver seat, i should be able to have decdent control over the sub's output without having to adjust anything on my receiver, and therefore screwing up the balance of my speakers, right?

The rear speakers are the least important in the vehicle. Leave the 4" out of the picture altogether.