6 subs up front in stereo?

I'm thinking of building kickpanels, placing my components in the kickpanels, and placing 6 or 6 1/2 inch subwoofers in fiberglass enclosures in the doors. I was looking at either JL 6w0's or 6 1/2 inch punch he2's (if you have any input on either speaker, please do post. Also, i'm only looking into these 2 brands since my existing comp's and coax's are JL and my subs are Rockford, and I would like to have the brands somewhat consistent). My main question is, is it at all important to have the 2 subs in the doors stereo? I understand that they will only play bass, but they are closer to the ear than my 2 12's in the trunk, so I'm assuming it would be just as important to have the 2 6 inch subs up front in stereo just as the components would be. Also, since my deck only has 2 pre-outs, would it be helpful to use an external crossover so the signal sent to the sub amp isn't affected? (or should I wait and invest in a Pioneer DEQ-P7000 5.1 processor) Deck:dvh-p5000mp

To answer your question about running the 6 1/2" subs in stereo; yes you should if at all possible, especially if they're mid-bass speakers since they'll be playing more than just bass guitar and drums.

Go for the JL drivers.  Definately use a stereo set.  Definately use a crossover and a dedicated amp for them.

Okay, so I should buy two 4 ohm 6w0's and find a 2-channel amp that pushes around 75 watts rms x 2. As for a crossover, should I just buy a 2/3 (2 input/3 output, where 1 input = 2 channels) crossover? I was thinking of just connecting the 6w0's amp to my existing sub amp using the rca out, and using the crossover on the 6w0's amp to block any frequencies it can't handle, but I know that Audiocontrol makes a crossover capable of 2 inputs and 4 outputs (6XS electronic crossover). Which would be better?

An external crossover is always better, especially in this case because you will probably end up wanting some mid-bass frequencies in the new JLs that you want to keep out of your subs.  I suggest running a good crossover like the 6XS and sending the front channel main signal to it, then low-pass an output signal to the JLs at, say, 180 Hz or so.  This should fill the normal hole in the sound between the effective sub frequencies (80 Hz and lower) and whatever you're using for front channel full-range (which usually are weakest below about 180 Hz.)  I use a set of 7" Scan Speak woofers for this precise purpose in my personal car and the difference was dramatic.

Thank you for the input everyone! Hmmm... is sound quality becoming more popular than loud @$$ bass? hahahaha, don't think that'll ever happen. I can't say I'm too old for loud bass, I'm only 20. (Wait, there isn't such a thing as being too old.) Let's just call it investment in better hearing when I get older.