SQLite: SELECT from grouped and ordered result

I'm new to SQL(ite), so i'm sorry if there is a simple answer i just were to stupid to find the right search terms for.

I got 2 tables: 1 for user information and another holding points a user achieved. It's a simple one to many relation (a user can achieve points multiple times).

table1 contains "userID" and "Username" ...

table2 contains "userID" and "Amount" ...

Now i wanted to get a highscore rank for a given username. To get the highscore i did:

SELECT Username, SUM(Amount) AS total FROM table2 JOIN table1 USING (userID) GROUP BY Username ORDER BY total DESC

How could i select a single Username and get its position from the grouped and ordered result? I have no idea how a subselect would've to look like for my goal. Is it even possible in a single query?