hey mate,
What model amp is it? TA3404, X704
basiclly, what you need to do is:
1. mount amp in boot somewhere.
2. Connect and run speaker wire, rca cables down one side of the car, whilst running power and remote wire down the other side.
3. Find a point to run the ground wire to (no longer than 50cm if possible) make sure you sand the paint back or it wont ground properly.
4. Connect RCAs and remote wire(blue wire on sony headdeck) to head unit.
5. Connect fuse holder to power cable (no futher than 30cm from battery), take out fuse, connect to battery (+side)
6. Mount fuse holder, and refit fuse
7. Turn car on, check amp is powering up ok.
8. Tune amp
not sure what else you will be able to run off that amp until you upgrade front speakers.