its 50w - 4x and So are u saying i should have a amplifier in the front and with the subs? and what channel amps?
What's custom about that deck? What I'm saying overall is that not even a $5,000 DAC will
not solve the inherent problems of a car audio environment. A stock receiver playing CDs or 320kbps MP3s with proper time alignment will still sound better especially when it comes to imaging compared to just using an audio player with a nice DAC (that opens up other ergonomic issues, like how it wasn't designed to be easily manipulated by one hand out of the corner of your eye while at a stoplight). Basically, save up, get the proper gear and proper installation, and don't go back to the times when the Discmans or MD Walkmans sat in the passenger seat with going into the cassette adapter.
If you are going to go for that kind of set-up, there are many processors out there like JBL's MS-One that can take a line-level signal from the stock receiver's speaker output (as well as an RCA input if your receiver has it), run it through an ADC, then through its DSP to employ time delays as well as the crossover points on each channel (still stereo, but each tweeter, midwoofer, and subwoofer gets their own signal out of it prior to the amp), then run it back through a DAC. GIGO principle doesn't count for much in a car when you don't address this, not to mention that these processors typically come with an autocalibration feature and test tracks so automatically EQ the signal to match what it should sound like in their acoustically-treated studio. My Alpine PXE-H660 has 512 EQ bands (separately for all channels) for its Audyssey autoEQ feature, vs what, a 5-band parametric manual EQ feature if I want to tune it myself. I have a DEH-80PRS with similar processing features but only takes CDs; with this new processor any car I buy - even with an integrated GPS - can have a properly-tuned system, although I'd have to stick with CDs or 320kbps MP3.
Now,
if that is what you will do, you'll need five channels of amplification. It can be either one 4ch amp or a signal, it doesn't really matter too much as long as you get something of good quality like Alpine Class D amps or JL audio. The wiring will then be like this:
Receiver --speaker/RCA output--> processor analog in--output stage --RCA--> 2ch for tweeters --RCA-->2ch of amplification--> tweeters
(stock or "custom") --RCA--> 2ch for midwoofer --RCA-->2ch of amplification--> midwoofer
--RCA--> 1ch for subwoofer --RCA-->1ch of amplification--> subwoofer
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As for proper installation of the tweeters and midwoofers, in very basic terms it goes well beyond Dynamat in your doors. These actually should be done first, regardless of whether you go for the processor above or not, since these can make a huge difference and a processor will only correct relative distance issues (T/A but also EQ),
not installations that have too many reflections in the cabin. The tweeters have to be angled properly as much as you put a toe-in with speakers at home, except this time instead of just width and depth you have two other concerns: soundstage height and managing reflections. That last part's the tricky one because if you put too much toe-in, the driver's side tweeter will sound more forward and the passenger side will sound vague or weak; use too little, and both tweeters will have too much reflections off the windshield, and the driver side will still sound more forward, the whole thing will sound sibilant until you really punch a hole through the treble with an EQ (the problem isn't the response, but you hear the same "t" or "s" several times over separated by microseconds). Midwoofers are less iffy an will require more extensive installations, although some isntall them on the kickpanel.
It would be best if you went on over to www.diymobileaudio.com instead of asking this over here where people focus too much on DACs and GIGO when that isn't the main problem. Also that's where many people who compete in EMMA and IASCA hang out (no, car audio competitions aren't all "let's see how many dB's your sub can...oh WOWOWOWOW look at your windshield! it's gone hahahahaha!"). That one is important because one of the things you can get penalized for is submitting a car that isn't drivable, so you can't jsut convert a car into a lounge room and win. Even my own Vifa tweeters will get deductions because you're supposed to avoid any modifications to the A-Pillars covering any part of the windshield.
Here's mine - in practice they don't get in the way but as per EMMA rules, that's a serious deduction for the install points.
And just a few more examples of what you can pick up from DIYMA:
Here the tweeter and midwoofer are installed in the kickpanel to reduce the variance in distance between them.
Here's one in a 3-way system - the tweeters I think (but I could be wrong) are the ones pointed roughly at the passenger on the opposite side, with the midrange on the dash pointing up. It depends on each of their own dispersion patterns on how they should be installed in order to integrate them better.
Here's a midwoofer in the door - notice how they installed it on the plastic itself, then reinforced that panel with fiberglass and a wood baffle ring. Some cars no longer have the metal frame to mount the speaker onto, not to mention that the soundwaves coming off the back of the speaker can reflect all over the door while the soundwaves coming off the front of the speaker don't just go out the door - some of it bounces back into the door causing cancellations and resulting in weak upper bass response that overcompensating with a higher cut off for the subwoofer will only result in wobbly bass that is easily located as coming from the rear. In properly done systems that are at least a fraction of what you can expect joining EMMA or IASCA, most of the bass should sound like it's coming from somewhere on the dashboard, despite the sub's location. This is because most notes comprise of frequencies produced by both the sub and midwoofer. With a proper time-aligned system you will hear the louder, more localizable upper bass "punch" or "kick" from the midwoofer at the exact same time that you hear the omnidirectional low bass from the sub in the back, which then reinforces that note as it would in a home system with the subwoofer in front.
