There’s really no point in having two fully-populated quadruples clues in a box. They only touch seven cells between them, so giving you four digits is overkill.

Rules:
Normal Sudoku rules apply.
Digits within circles appear at least once in cells touching the circle.
Sudoku-X: The marked diagonals each contain the digits 1 to 9 exactly once.

Estimated difficulty: 1 out of 5

Solve on SudokuPad
Quad Marks the Spot