Best Amplifier for the Job

For the best ratio of power output vs. power required (efficiency of the amp) to run the amp, you should use a one channel (mono) amp.  Since you'll be running it at 4 ohms, look at the power output rating at 4 ohms and match it somewhat closely to your sub's continuous power handling in watts.

Now here's where it gets just a little bit complicated.  You have the alternative to use a two channel amp and bridge it to power this sub.  The amp class is of a lower efficiency than the mono amp so it might take a little more of your car's power reserve to run it.  This would probably be the cheaper route to take.  Look at the bridged output rating at 4 ohms to do the matchup with the sub as described above.  As you can see, either one will do the job, but the SQ goes with the higher impedance per channel, which would be the mono amp.  This is where the complicated part is:  bridging two channels puts half the load onto each channel, so that is how the amp will operate.  A two channel amp powering a bridged 4 ohm load is powering that load via 2 ohms per channel.  The result is a lower overall quality of output (than powering at 4 ohms per channel), although more power is produced.