[MonteSS454]

I would say the old amp won't do you any good.....it probably still works but if it's old its no good to you.

Try running the 6x9s and 6 1/2s off your deck,
Left Front - Rear
Right Front - Rear.
6 1/2s on the Front Left/Right wires.
6x9s on the Rear Left/Right wires.

Then go find yourself a good 250-400w Monoblock (1 channel) amplifier to run your subs and it should run just fine.

But, if you're worried about drowning out your speakers, turn down the gains on your amp and through the deck so you don't drown out your vocals.

How much are you willing to spend for a good single channel amp?