Adding Amp to Factory Radio

Planning on using an AudioControl LC21 and running an amp to power the rear speakers and a sub/subs. I'll let the radio power the dash speakers. What kind of amp, channel wise do I need? And power wise. Don't need crazy loud, just better than what I have now. Of course, I could skip the subs and just use an amp on the rear speakers. I'm using an early 90s Delco CD player w/5 band eq. Any thoughts??
Any modern quality amp with speaker level inputs is going to work. Pick based on form factor and features.

Splicing in at the head unit behind the dash instead of running new wires all the way to the trunk is the way to go. You can build an adapter harness and not have to cut any of the original wiring for the speaker runs.
To run a pair of 6x9s and a small sub or 2 do I need 4 channels?? Planning on the radio powering the dash speakers.
If you're going to put the amp in, it's very little additional cost to get a four channel and run all the speakers off the amp. The head unit won't be able to keep up, so if you run the fronts off of it, you'll never hear them again.

Unless you really want that sub. You'll be surprised how a set of good 4x10s with some actual power sound. You might not want the sub... unless you're aiming for hood-rat levels of shove. Maybe stage it. Do the four channel with replacement factory location speakers and some power. If you want more, add a self powered sub.
Not sure about the sub yet. I've had 10s and 12s before and don't like the bulk of a box at all. I just want a simple, affordable system w/more gusto than it has now. No ghetto bump-bump for me. Thanks for the replies.............

1986 Buick GX1

GX1 #001 [The One and Only]
When I first put an amp in my car with concert sound II in '88 I used a two channel line level converter in the trunk on a Crutchfield (PPI) 20 watt (RMS) x2 amp and pile driver 4x10's with the fronts and doors ran off the stock stereo.

I felt the 20 watt amp in the rear made all the speakers the same level at the drivers seat (gain knob at 60-70% and stereo fader in the middle) with enough punch to fill out the lower end.

I would say it was similar to a 6.5- 8 in sub. Not loud, just nice.

In comparison, I had some 6x9 Infinity reference speakers in the rear of my '90 Regal with a Crutchfield 50 watt RMS x 2 (gain knob at 60%) using the stock stereo with a converter that people thought I had some 8" subs in the trunk.

I have one of these four channel converters in my '94 Cutlass Supreme Convertible hooked to a 40 x4 (RMS) at 60 % gain for the dash and door speakers and a 50 x 2 (RMS) at 50% gain for the rear side speakers with good success.

I'd have to look to see the gain setting on the converter, but I think it's around 50%.

It's got (4) gain controls, (1) for each channel and built in ground loop noise isolation. You could connect it pre-amp and run it to a 3.5mm aux input, although the volume would be controlled solely off the device.


The audio control lc21 looks like a nice unit, probably better quality than mine.

Try to get an amp with no more than .05% THD for good sound. More than that, you'll get some background hiss. Less than that you won't notice a difference over your exhaust and turbo whistle.

One thing to remember is the the stock stereos start cutting bass at 75% or so.
If you set max volume at 50- 60% volume you'll get much better sound.
Update.....bought a MTX 8" self powered sub tube RPT8T and hooked it up using the high level inputs from my rear speaker wires. Install went easy enough. Sounds really good and this is all I want for now. Adds lows that were not there and a little kick too. I'll hold on to my level converter for now. I would recommend this sub. 150 bucks to the door w/wiring kit bought online. Easy hookup. Also has a small bass level control w/light that mounts in cab.
OK, upon investigation,the dash speakers were falling apart. The foam was rotten. I found some inexpensive 3.5" speakers at AutoZone. Raptors I think. Hey they were cheap and fit. I wired in some bass blockers at the same time. Wow! Sounds really good for the money. Pioneer 4X10s in the rear deck were still good. If they need replacing in the future I'll consider some 6X9s. The bass blockers work. I've heard about them for years but never tried any.
The bass blockers I got off Ebay. They have them for different sizes of speakers. They just wire into your positive leads. They were reasonably priced.