If you have the Bose system, and want to keep every thing factory but just change the Amp and buy a EQ........ what will be the wise choice of Amp and EQ for the factory HU and speakers?
Please advise...

 

I would highly recommend changing the speakers as well. Factory speakers are almost always the weakest link. If you want to keep the factory head unit, you will have to wire in line-out converters on your speaker outputs, then patch them into the amplifier. Converting from an amplified signal (with all the distortion introduced by the headunit's internal amplifier--on a side note, headunit amplifiers have insanely high THD (total harmonic distortion) ratings) then back to line-level outputs to patch into an amplifier introduces huge amounts of noise and distortion.

Further proof: A friend of mine decided he wanted to keep his stock Honda Civic headunit ("because it's an Alpine!") and wired in line-out converters into his rear speaker lines, then patched those in to a Fosgate (decent amps) amplifier running an Infinity Perfect 12" (also decent). It sounded like ***.

He later changed out all that stock garbage for a nice Pioneer headunit and Pioneer speakers. Too bad he had to toss the Alpine CD changer he bought to connect to the stock H/U. It sounds so much better now.

Note that amplifiers with "high level inputs" just do the same thing, resulting in the same distortion and noise.

Anyway, my recommendation, if you want to upgrade your stereo, is to either do all of it, or none at all. Adding upgraded components and discovering later that it didn't help is a horrible feeling and waste of cash.

 

Also, be aware of these issues on the Bose unit:

1. The Bose deck does not have amplified outputs, and requires a special differential converter (rather expensive) to allow it's use with aftermarket amplifiers.

2. You will have to replace all the speakers also, as they are a special low impedance speaker designed to work with the Bose amp. If not replaced, you will be very dissapointed with the sound quality with an aftermarket amp, and the amp won't like the impedance of the speakers either.