So i have an Alpine INE-W940 6.1 HU on order along with a backup camera, dash kit, and XM unit on order for my car. I need some tips on a basic decent sounding audio system without spending another 1k... What kind of amp do i need to power all speakers and the sub in the back? i want to keep the speakers and sub stock for now but i have read that i shouldnt use stock amp with aftermarket HU.... I am completely new to the amp portion of this upgrade... so please i need all the info i can get... also does anyone have a good link for a wiring harness that will fit this HU? BTW i have seen some write ups on how to do this but none on what components to get... in the future i want to upgrade speaers to kicker with a kicker sub that dosnt require a custom box... i want the car to look as stock as possible except for the HU... everything esle needs to be hidden... Thanks for the help

match your amps with your speakers both in ohms and wattage (RMS)
4channel amp (digital/analog doesn't matter) for your door panels
digital monoblock for your sub

i think stock in all 4 of the doors is 4.25"
i used these
http://www.speaker-installation-photos.com/Lexus/GS
to go 6.5 all the way around. components in the front (tweeter fit perfect in stock location), coax in the back (popular opinion is that components in the back are useless).
i have a 10" w/ ported box in the trunk that sits well on the rear shelf where the stock sub+amp used to be

wiring harness get it from metra

you're gonna hafta convert from stock serial amped to RCA in this car

oh forgot to add you'll want a nice fuse holder (i went 200), a capacitor is optional (i've got one 2.5), maybe HO alternator, 4gauge minimum wiring a must

you can run your stock amp just fine all i did was put a resistor on each + speaker line inline from the deck harness to the harness kit

the resistor's i used are 62 ohm 1/4w 5%

please dont run stock amp with aftermarket subs..

offbad is pretty much dead on. you can fit 6" all around and run tweeters and components

run a separate ampto all the door speakers and if you really want you can get a box in the trunk and run another sub

I want a sub to put in the same spot as the stock.... Would a kicker comp 10 work?

sure i guess
most subs aren't built for infinite baffle unless you're gonna fabricate a custom box the output might not be what you're looking for.

in general:
sealed-- easy install, small space, "tight" response
ported-- easy install, takes up more room, more response but can sometimes be considered "sloppier" response
IB-- no box, no room to take up, need to find right subs, output may be "lacking"

it's all preference really. best bet would be to hear side by side comparisons, limiting your variables, and hearing what you like.

I'm really not looking for an extreme amount of bass... Just enough to sound nice... Don't need to rattle the trunk... Can you point me to a diy to use stock speakers and amp with an after market head? I can't quite afford the amp, sub, and door speakers yet...

If you've already decided to go completely aftermarket with your audio ie your Hu especially you might as well hardwire your existing speakers seeing as there still good and your going to have to do it anyway to run aftermarket speakers....so picking up a 4 channel amp to run up mids and highs in the mean time that can be done cheaply and still have your stock sub as well getting a little more juice to get that bass your searching for...personally I've found my 99 gs 300 to be a challenge having been a professional installer in the past but if u r a novice or like me prefer run your set up how you would like rather them follow what the manufacturer has installed lol....sometimes the simplest and cheapest way is the best solution...In this case getting rid of stock amps and wiring all together.

Pm me if you need help with your install

What i really want to do to start is (for now) run aftermarket HU with Stock amp. Then later on when i have more money upgrade to the 4 channel amp and aftermarket 6.5's and tweets... so for now my basic question is: is there a harness or adapter that i can buy to go from aftermarket HU to stock amp? Or do i have to do some modifications to the stock wiring?

You can do it but it is a pain I'll look into procedures for you I've done it with bose&other stock amped systems before sometimes it just involves like you said a few adapters or looped signals....you have a namikatchi system right now correct or stock

Interesting. Can he/I keep the stock 10" woofer and just power it with an aftermarket amp?

idk what i have... i have the 2000 gs300 platinum with ivory interior (like it matters) but if i absolutely have to i guess i can get a 4 channel and a monoblock and just tap into existing wiring.... its crazy i do avionics work in airplanes all day long but dont know the first thing about car audio... but i can make some pretty connections and i can solder like a pro!

from what i understand you can but is wont sound so hot... but another guy on here replaced his sub with a kicker comp 10 (but kept stock amp) with minimal trouble...

Stock sub on aftermarket amp is possible but useless it'll blow very quickly from over powering....Also the 2000 gs...If you run aftermarket amps to run ur system it's recommend you hard wire to the door speakers stock wiring isnt the best for aftermarket applications and obviously doesn't run to your trunk...Two choices is to spice factory wiring before the door or run ur own....more work to run ur own but worth it in the long run....