I want to install some reference 60.5CS in the door. I might want to get a small 2-channel amp for them, but I want to keep the stock head unit. Anyone have this setup and where should I put the amp, suggestions? Thanks.

 

I'd upgraded my car which is MY04. I kept stock HU, and upgraded/add the follwing:
Door speaker: Kappa Perfect 6.1
Rear panel speaker: Kappa 52.5i
Bose Sub in spare tire well
4-channel Memphis Amp 50Wrms x 4, under driver seat
4-channel Line Output Converter PAC OEM-2

If you want to keep the stock HU and add a small 2-channel amp, you will need a 2-channel converter if the amp you buy do not have speaker-level input, because stock HU does not have RCA output. If you want to install the amp under driver seat, the size should be limited to: 12"x8"x2.25".

You can read more about how I done mine: " Stock HU + Amp + Kappa Speakers + Bose Sub"

 

I bought some Eclipse 8952 so I can drive it with the rear speaker outputs of the HU. Since the rear is just fill, will it be sufficient if I don't use an amp, and just a 2-channel for the fronts? Or will there be a big improvement if I also amp the rears?

 

This has been a running debate in this forum. It is my belief that you do not have to amp the rears. The stock HU for the '04 should have enough power for the rear fill. An upgraded HU is an improvement. I would get a four channel amp and instead of amping the rears with it, i would amp the fronts and a small sub. Not for ghetto bass, but for a low end that will improve any type of music, be it classical, rock or country.

for those speakers, IMO you won't need an external amp.