So heres the deal, i want to upgrade the shaker 500 system i currently have. Current list of equipment in my possession:

Alpine Ida-x100 source unit
Elemental designs 6.5in components
Polk MMC570's for the rear
Rockford fosgate p450.4 amp

According to the specs on the amp, the front and rears would be seeing roughly 92x4 @ 4 ohms.

Do you guys think the factory shaker subs would blend in well with this combo or do you think i would be happier with a seperate sub in the trunk. I am not looking for earth shattering bass, just a well rounded system with some thump.

 

Here is a breakdown of the system I recently put into my 07 Coupe.

JVC JW-AVX810 (Double Din Touchscreen DVD Player)
4 Pioneer TS-A6882R Speakers (4-Way 6"x8")
Kenwood Amp (800W Max)
2 Pioneer 12" subs (1000W Max)

I am VERY happy with my Double Din head unit. It isn't the best one around, but the sound is great and a Double Din touchscreen looks AMAZING in the dash of the mustang. The Alpine units have a much FASTER IPod interface so if you want IPod control at a very fast speed, stick with your Alpine. I got my JVC for $500 on Ebay. Just a thought.

As far as sound goes, I am just like you. I don't want all the neighbors to know what I have in my car, I just want it to sound great on the inside, I dont care what the guy next to me thinks. This is why my amp is low powered. If you want to use the shaker subs just to compliment the speakers, it will work fine. Just make sure that your head unit has a Subwoofer Preout. Then connect your Shaker RCA's to that output. You will have complete control over the woofers with that. But, there is a drawback. The shaker subs are not connected to the door of the car. They are only connected to the door panel. When the shaker subs hit hard, you get a LOT of rattle from them. Every little piece of plastic in the door will make some noise.

Here is my advice. Dont even use the Fosgate amp. If you have a good head unit, you wont need to. Just get 1 sub for your trunk and an amp that is around the same max wattage. I will be removing my 12" subs soon and replacing with a 12" shallow mount sub for the trunk. I will then bridge my amp and put all 800W to this one subwoofer. This will give me very clean bass on the back end and I will get all of my highs and mids from my interior speakers. In my opinion, amplifiers for interior speakers are much better for convertibles and cars that are going to enter sound competitions. I have always been very happy without an amp to power my interior.

My head units volume goes to 50. When I turn it up to 30, you can hear my system from down the block. Hope my opinion helps.

 

The 4 ch amp will brightin up those speakers. The factory subs may not be able to keep up with them.

Speakers(mids and highs)on an amp will sound soooo much more cleaner, then just running it on an aftermarket deck. You will get alot more volume and will not have much or no distoration from those speakers on an amp. With those speakers just on an aftermarket deck you will maybe be able to turn that alpine deck to 25 volume before it starts to distort, with an amp you will not have that distoration.

If any thing get yourself some new 8" woofers with an amp. You will not loose any trunk space and still have a great sound.

 

just my 2 cents..... i have an old school orion hcca 275 g4 running my stock 8' in the doors and they sound great.... i have the gain all the way down .... but they still take the power.....