You could also run the remonte wire into the fuse box and loop it into the ecm ignition fuse, its a bit easier than taken the radio off...
to hook up the amp just go buy the rca converter( cost about $10) tap into 6x9 and thats it. its fairly easy and it wont mess with the sound of the 6x9 too much.

 

OK, First, Hi and Welcome!
I would splice the speaker wires from the back of the Radio to the amp. This way there is not distortion in your 6x9s . Second, Run your power wire to the amp from the Battery with it's own inline fuse, You don't want the amp to blow any of your stock fuses. Lastly, You can go to RadioShack and get Fuses with a Pigtail. Get a fuse to match any of the fuses in the car that turn on with the key in the Aux position. That way your amp will turn on and off with the key. Also, when you plug to new fuse in, the one with the pigtail that you hooked your remote wire to, Make Sure you put the Pigtail side on the Always Hot side of the Fuse. This way, the remote switch draws its power before the fuse and rules out and small chance of the amp blowing the fuse.
This is the best way to go, IMO!!!!!