I agree. If you can afford it, test. We were faced with a similar dilemma. A friend who also has three gifted kids told me to go ahead and test for the following reason: If you don't test, then that kid will always think that you don't believe he/she is as gifted as his/her sibling. Also, I've had several friends who assumed that their second was not as gifted as their first (maybe due to birth order differences?). After testing, the second was the same if not higher than the first.