Which way better for front sound stage?

I would like to get some opinions on how I should change my setup as far as the front sound stage goes. I currently have some lower end Polks in the dash and the front doors. I feel like the low end of the music spectrum is lacking something, so I was thinking of changing the setup, but I'm going in circles in my head trying to come up with something that will work the best.

So here are the specs - 4" coaxials in the dash; 6.5" coaxials in the doors; 2002 GMC Sonoma Extended cab with an old school Alpine head unit. The speakers are powered by dedicated amps and are getting 30 watts per speaker. They are all crossed over at 80 or 85 Hz HP. The 4"s may even be crossed over at 100 Hz, I don't remember exactly how I set it up. The frequency range on the 6.5"s are 70-20000 Hz, and the 4"s are 90-20000 Hz. The low end is handled by 3 JL Audio 10W6's.

Here are the 2 options I was thinking of:

1) buy the JL Audio XR653-CS 3-way component system. The 4" mids would go in the dash, the 6.5" woofers would go in the door, and the tweeters would need to be custom fit in the doors or somewhere else. Would this even sound right?

2) or just buy better coaxials for the doors and the dash and not worry about having to cut any holes in the doors or dash for tweeters.

One last thing I am tangling with - which brands to buy. I'm trying to choose between JL Audio, Infinity, Boston Acoustics, and MB Quart. There are two or more shops fairly close by where I can get any one of these brands, so that is what I would like to stick with. Which should I choose for my spplication and why? I know that I should audition them myself, but I would like to get some objective opinions first before I do that. Having been an active member here for some time, I have read quite a bit about some of the pros and cons of each brand (except maybe Boston Acoustics), so I'm just looking to see what else some of you might have to say.

Thanks for any help provided!

My suggestion; drop the 4's in the dash.  Having 2 sets of speakers up front will cause nasty comb filtering, and really won't do much to help your sound any.  But it is best for you to make the final decision, so I suggest listening to the system without them for a while and see how it sounds. 

Here's my personal opinion about the speakers you list.  I have always found MB Quart speakers to be way too bright, almost shrill.  All the Infinity sets I've heard seemed to lack midbass.  I've never really listened to the other two carefully.  I was kind of unhappy to see one design issue on the higher end JL set.  To make the crossovers more cosmetically appealing, they placed all the coils lined up in a row.  This creates nasty cross-talk that can color the sound. 

Ok I guess my last post was deleted....  Don't really know why.   If somebody could advise me why I would appreciate it.

But what I asked in it was if you had checked out the new psychoacoustic bass controller.  I have heard good reviews about it, and it is supposed to improve the perceived bass response.

I was replying to this quote.

Have you heard the technology killer sonata?  or are you just saying that because it sounds like b.s. technology?  I have not personally heard it so I cannot give an opinion, I was simply informing him.  I have read about it on the wavescaraudio website and it sounds like interesting technology.  If I remember correctly it was/is used in cathedrals where they could not fit a large pipe organ, but they still wanted low frequency extension of a large one. 

Please let me know if you have had an experience with this technology, as I have not heard a review of it from anybody on this forum.

Thanks for all the responses so far. Keep them coming.

What I meant about the "low end of the music spectrum is lacking," I was meaning the midbass/midrange seems weak and overpowered by the rest of the system. Since the speakers I currently have are limited to 70 Hz and higher by the speaker itself and I have to run the crossovers higher than I wanted to, I think this may be the reason why.

So I'm guessing that the 3-way system as I've outlined it would not be a good option? It essentially takes the 4" coaxials out of the equation while upgrading everything in the front soundstage. Make sense?

Thanks again everyone. Giving me lots to think about.