Skip the Slash Series, too expensive and very inefficient. I would go with the maybe an Alpine M12, which is a bit expensive, around $500, but would give you the power you want, even with the weird ohm load. And thats a new price. Or even an Alpine MRP-M2000, which would give you 2k @ 2 ohms, which with the 3 ohm load you have, and the gains a little down, would be very sufficient! It can also be had new for about $425.
Those are just some ideas. Of course you can get the same amount of power from some cheaper (less expensive amps).