I think those hinges would be beefy enough, but it will probably look like a shed door.
I still think the way to go is to add layers and seals to an existing door. Here's a basic exterior steel slab door for $105:
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There are plans for beefing up doors in "Home Recording Studio: Build It Like The Pros" by Rod Gervais
Amazon.com: Home Recording Studio: Build it Like the Pros: Rod Gervais: Books
Good Luck