If the Bitcoin symbol is placed before the amount I will think that it's another version of Bitcoin, When it comes to the currency we are used to placing it at the start of the amount so it's just right that the symbol be put at the start of the amount.

When I was active in the Bounty campaign there was an altcoin there that was named BTC2, and they call it the new version of Bitcoin, we also have Bitcoin2 in the market https://www.coingecko.com/en/coins/bitcoin-2-0.
So to avoid confusion it's better for the symbol to be placed before the amount.