Audio Systems: amp wiring, ford mondeo st, mondeo st tdci

Question
alright mate, I drive an '06 ford mondeo st tdci (UK - i'm from scotland) and have a sound system from my old car, new car stereo has no pre-outs and i've heard you can wire amps off of the rear speakers, problem is only one of my amps has capabilities of speaker level input. can i wire these in such a way that they both work? (even opening other amp up and soldering).  If you could help me out here i'd be delighted, cheers Stewart.  

Answer
If you use the speaker inputs the 'amp' becomes a basic power booster and not an amplifier. Ty to avoid EVER buying an amp that has speaker level inputs.
You can buy speaker level to line level shunts but again it is really alot of work for what wil be a poor sounding and noisey system. Get you a new headunit with line outs. You will be much MUCH happier with the end result.

Jerry Mael