3 12 punch hx2's

First, determine what impedance load you'll get by wiring these three subs together.  Use the woofer wiring wizard in the left column.

https://www.the12volt.com/caraudio/woofer_configurations.asp?Q=3&I=42

With a load of 2.67 ohms, this rules out using a two-channel amp whose lowest bridged load is 4 ohms.  This means you should look for a mono amp.

Now, what is the continuous power handling / thermal rating / RMS rating of this particular sub?  Multiply that rating by 3 for three subs.

You know you have an odd impedance load of 2.67 and that the amplifier specs will give you ratings at 2 ohm and at 4 ohm.  Find the middle ground between those two ratings and you've found the output at 3 ohms.  That's very close to 2.67 so you can use that number as your guide, and find a mono amp whose output will give you enough to match the RMS of the subs.  The amplifier's output into 2 ohms will be higher than the total RMS of your three subs, and its rated output into 4 ohms will be lower than your target number.  But at what you figured the 3 ohms output would be, it should just about match the subs' total.  And you can always go a little less power.