Okay, my bad. Though we're making DSOD happen a year after the events of GX, in our story. Now that you've mentioned, it would goes as follows:

Yugi
• 16-17 (original and GX)
• 18 (Dark Side of Dimensions)

Jaden 
• 15-16 (original and GX)
• 17 (Dark Side of Dimensions)

Yusei 
• 18-19 (original and GX)
• 20 (Dark Side of Dimensions)