The beauty of her gray eyes

In the second sentence below, what is the appropriate punctuation after the word "hear"? Must I use a comma? Would a period be all right? What if I left it without any punctuation? Also, is the dash used appropriately? I didn't want to use a comma because I wanted to emphasize "loudly enough for others to hear."

He marveled at the beauty of her gray eyes with their long lashes, and became lost in a reverie of adoration. Without thinking, he sighed to himself—loudly enough for others to hear, “She’s got eyes, ain’t she?”