will they go louder

Sounds like you might own the wrong speakers for your son to enjoy. Magnepans look like they should play at ear bleeding levels, but my experience is they wont in large rooms, or if you sit past 8ft from them. For reference I am speaking 98-100 db's or more.

Do you have 1W/1M spec of your speakers? Then calculate the theoretical max SPL of your system at 1 meter with the amps you have (it will be less due to room absorption). Then starting at 1 Meter, calculate -6dB less for each doubling of distance to your listening position; this is the theoretical max SPL of the system at your listening spot.

Maggies are not point source speakers -they are dipoles- so the rules are a bit different. At least this can help you get a rough idea of what's happening.

Can you lower the amp gain controls so your son cannot drive it to full output (the fuse popping point) using preamp gain?
Brad

my 3.6's register up to 100db and they are a great rock speaker, they require great amps and tons of power

No really stay with the recommended fuses. You might just move your listening position closer to the speakers. More volume and cheaper then new speakers.