Good thought, but it's not necessary to trim the carpet under the amps. Unless you are mounting the amps upside down with the heat sinks/fins on the carpet, this won't be an issue. Some older amps (phoenix gold ms/mps series) had cosmetic plexiglass covers so you could mount them upside down to display the internals. That type of mounting could be an arguement for (maybe) trimming the carpet.
If you are truly concerned with this, I'd recommend you use some small (1/4 inch) spacers to raise the bottom of the amp off of the carpet slightly. However, if the amps heat sinks are exposed and have free space to ventilate, proceed without worry. These spacers will also allow you to tuck the wiring under the amps and pass them through a hole in your mounting board. Makes for a clean install.
Get some pics up when you're done, and good luck!
Alan