My system sounds like junk

I recently purchased and installed an alpine head unit with two 10-inch infinity sub-woofers and 4 side door polk audio speakers. On paper, one would think that it would be a pretty decent sounding system. However, I'm very disappointed with the sound. I primarily listen to fast-tempo rock music. The deeper chords are very weak (mid-range lows). The bass isn't punchy enough. The deeper bass sounds are overwhelming and the mid-range bass sounds are weak as hell. Any suggestions for adjustments? Frequencies, ect.?

are the speakers ran off the head unit because that will more then likely be the reason because the speaker can't act like they are suppose to.

The polks are hooked to the head unit .. The subs are running off of a 200 watt 2-channel amp.

as far as the overwhelming bass from your subs, if you're not using an separate amp for your door speakers,
then you're going to have to match your amplifiers output to your head units output. This is how I would do it...
1st turn off all the signal processing on your radio and amp including loudness, bass boost, compression and equlizers, (set bass and treble to zero)
turn down the gain on your subs amplifier, turn up your radio to about half way, then slowly turn up the amps gain to match the door speakers output
once you got that matched up, then you can use the signal processing to shape the sound to your preference, I usually start with bass and treble

amplifying your door speakers will make a HUGE difference in your sound system
if you decide to amplify your door speakers, they'll not only play louder at higher volume levels,
the sound will be fuller and richer at all volume levels and your sub amp will be matched at a much higher level...

makes sense, and thanks for the input navy, however more than anything i am looking for more punch .. better, fuller sounding power chords for metal bands .. it is so weak-sounding right now .. i feel as though i need a stronger amp for more mid-range bass, then i could turn off the bass boost to tune down the low frequency bass sounds and i'll still have a fuller mid range .. more powerful oomph to it. very disappointed.

a separate amp for your door speakers will definetly help.
You know what else you could do, you can run a full range signal to your subs instead of just a sub signal...
The full range configuration takes a different type of tweaking, but you can still make it, "do what it do"

you don't really want to use bass boost. here is an example of what it does to your signal.

http://www.icixsound.com/iv/view_video.php?viewkey=c13838ff95ccfa94cebd&page=&viewtype=&category=

you need a 4 channel amp for your mid/tweet speakers, then you will have to tune them. Midbass is usually the 75-150 Hz range or so, you will need some power on the polk's if they are mounted in the doors (known as infinite baffle).