I don't know, I don't do AEGs. I do know that Siegetek gears are by far and away the best on the market though.
From what I have read, something around 20:1 is good, pair that with a Terminusx motor and you're good to go!
EDIT: Don't forget the Terminusx Bushings...hell, just buy every product you can from terminusx besides the gears (which you need from Seigetek).