The reason people are trolling you for your 'bad knowledge' is because all the knowledge you seek is right here on the forum, you just need to read it.
There is no such thing as the 'best sub' they all have their pluses and minuses.
You don't mention which model sub or which movement you are looking for, this is why you need to read stuff and form your own opinion.
The latest Noob V9 and ARF are $500, so outside your budget.
The VRF is more within in your budget, as is the Noob V8. Don't forget there are shipping costs on top.
You just need to read and browse the Trusted Dealers websites, we cant choose a dealer/model/movement for you.