Well that's great! I really appreciate your response. You've been really helpful.

I'll keep watching the price on the HU for now. I'm thinking of getting an upgrade from OEM in a few months. I think I'd be okay with just buying this HU, Kicker 40CS654 front speakers and amping those with the same amp you bought (Alpine KTP-445A) and leave the rear speakers alone. I should be okay

Infinity speakers run at 4 omhs just like everyone else. They measure it by including the wiring to the head unit.

If you watch Crutchfield they will occasionally sell open box/return items for cheap. That's how I got my HU and it was $30 off just because the box was opened once. Amazon does deals like that as well (Amazon "Warehouse Deals") but they go so darn fast because people are watching for those.

Installing an Alpine HU with the small little Alpine amp was the easiest wiring job I've done in my whole life. Literally plug and play, I don't think I'll ever buy another kind of amp from here on out. Only hard part is figuring out where to put the amp, depending on what year/options you have it can have more or less room back there behind the dash.

I'm not sure what you mean about the wiring to the head unit. That would not affect speaker impedance. Not all Infinity speakers are 4 ohms. For a few years, they intentionally made the Kappas 2 ohms with the idea of getting more power from an amplifier. Some head units were not happy with the 2 ohm impedance so they would shut down when turned up.

The Kappa line was not designed to be run off a head unit anyway, they were designed with external amplifiers in mind.

I believe the current model Kappas are 4 ohm again.

Either way, I wouldn't recommend them personally. Their tweeters are too aggressive or "bright" for me.

Any pictures of the deadening of the cargo area?

Not trying to bump my own stuff, but wanted to add a final thought or two.

A year later and I still love my sound setup, works awesome and sounds even better. Have it tuned in pretty good to how I like it. If I were to change anything I did, I would add sound deadening on the driver's and passenger's side foot wells. That's the only area I have sound bleed now that's significant. So if anyone is planning to do this, add that to the list! I only did the fire wall as far as I could reach and I wish I had just done an extra few feet more down to the seats. Still sounds great though.

I dont disagree, the rear speakers are important to fill the truck with sound. It's the non-audiophilies that have no clue.

One of the biggest things is the damping factor. Basically it's a measure of how well the amplifier is able to control the speaker cone. Head units are typically limited in this regard because their output stages are limited to about 13VDC (input power from the vehicle). Amplifiers use a DC to DC converter to raise the voltage a lot higher, and that allows the output stages to be designed to have more control over the speaker.

The problem is, when you start doing the DC to DC conversion you add heat to the equation, and pretty quickly you need heat sinks larger than would be practical in the space a head unit has to occupy. Some of the higher powered head units are doing it, but they still can't use the large components needed to match the performance of a typical external amp. The DC to DC conversion requires a lot of internal filtration to keep it clean. That's why you see lots of large capacitors inside high quality amps.

In the photo below, nearly everything in the upper half of the amp is the DC to DC converter. The things that look like donuts wrapped with wire are toroidal transformers and you can see the banks of capacitors next to them for filtration. The lower half is the audio section. If your car could supply a clean 50-60VDC to the amp, you could get rid of everything in the top half.

sorry for bringing up this thread.
with regards the door cards, is it better to use the foam-type insulation like you did, instead of using the dampening-type of insulation (the one with aluminum backing)?
I haven't done the door cards yet but I'm planning to, so I'd like to know which is the better one, acoustics-wise.
Thank you.

It lives!!! Back from the dead.

Yes, the two pieces have different uses. The dampening type made of butyl or rubber mat with the foil backing is used to absorb vibrations. It is placed on exterior metal sheeting like the doors or on the floor or roof. By absorbing vibrations (also known as noise) that come from the tires, engine, etc. it reduces the noise level in the interior as well as providing a cleaner sound from the speakers which also send vibrations into the metal. It is normally placed right behind the speaker so when it fires the sound doesn't bounce around in the door like a tin can and instead it is absorbed by the mat and you only hear the sound being projected forwards towards the passenger.

The foam insulation is used muffle out all outside sounds. Because it is just foam it does not do a good job of absorbing vibrations but can be used in tandem with the rubber mats. A pro installer told me to put a layer of matting and a layer of foam behind the speakers in the door as well as anywhere else it fits. The more foam, the quieter the interior. I was also advised by some posts on here to do a DOUBLE layer of both foam and matting in the rear cargo so mat - foam - mat - foam. The rear cargo area is by far the noisiest part of the vehicle as so much sound comes up from the rear wheel wheels and cargo pan.

A side note - I overdid the foam on the top orange part of the interior door card, as you call it. The lower half really needed it but I had lots of squeaks after doing the top as it bulged and rubbed on the dash. I eventually took the top part off and left the foam only on the plastic bottom half (the orange looking material acts as a sound insulator anyway).

thank you for expounding.
may i know the thickness of the foam that you used for the plastic door panels?

Great write-up! Just bought a 2002 and a similar project is in its future.

What @gamefreakgc said post 100.

I did foilback 2mil thick mastic top to bottom side to side front to back,
1/2" thick foilback foam above headliner, cargo area rubber mat, residential carpet pad, cargo area carpet, OE accessory carpet mat,
queen size egg-crate 1-1/2" mattress pad here n there. Needs more.
This time every nook n cranny between inner body panel and outter body panel
C pillar back getting stuffed with foam, doors another layer.
My second go round is basically his using of layers of foam in right spots & foiilback mastic or not.
Get that right the first time your GtG.