With my audio background just share a few tips.
On MDF i have NEVER used screws to attach anything.
Use timber TTE NUTS that way you can use a small bolt to attach the amps.
This way you can remove any time , how many times and never thread the timber.
Also secure the MDF to the body by using SIKAFLEX 255 Top stuff.
Now if you mounted it under the seat you could use very thin MDF 6 mm glue it under the carpet with the TEE NUTS on the corners. Then add a couple of washers and have the amp suspended off the carpet.
Also tiny slit and have all the wires hidden.
Just a thought. Out of sight out of mind