You should buy a Skar 1200 watt monoblock class D for your Alpine subs. Alpine Type R subs would be my choice..Purchased from Amazon
is under $125. I'm sure you'll like Skar amplifiers and buy another from them again. Be sure to wire both subs correctly at 2 ohms or even 1 ohm to experience unbelievable lows.
Currently I'm running a Skar 12" dual 2 ohm voice coil sub with a 4500 watt monoblock amp. I connected it at 1 ohm with 0 gauge copper wire. My amp at 1 ohm will produce true 7000 watts and make a fire inside the car if I go full power. I will get pulled over and a ticket if I'm bumping it!