Id say use one for your front battery maybe. I picked up at Red Top from a buddy for $50 and I think it was well worth it. Starts up the car easily and quickly every time even in 0 degree weather this winter. I have pretty decent voltage too with a stock alt on a first gen Neon so prolly not so many amps from that maybe 65-90A if im lucky and all engine grounds and BIG 3 in 4 gauge pure copper (I know not 1/0 yet...) and my voltages at idle (900-1050rpm) drops to lower 13s at full tilt at the lowest so Id say it can put out some juice. The amp is rated at 1200rms and fused for 120amps running at one ohm.
Anyways Id say scoop up one for the front or if you want to I think you could use the others in the rear but there is better out there and if I took the money you would pay for 5 of the redtops at 70 bux I would have 350 to spend on an excellent battery or two very nice ones.
Its up to you in the end and what kind of rms wattage do you plan to be running?