Hey, mate

I like your decision to build your hifi rack making use of the Maple butcher. It is a popular choice and the one that my dad made use of when he constructed the hi-fi rack that we use at home.

It can be able to carry the heavy amps without issues and although it costs more, the quality is always assured. I didn't see you mentioning isolation feet, but it is what you would need under the rack for stability.

I believe that spending $900 or around that price can be able to handle constructing a strong hifi rack for all your sound components that you use at home. I mean the wood would cost around 500 dollars or thereabouts while the cost of the frame won't cost more than $200 to get everything. So, you are within budget.