Portal is the game we are considering for DS8. It has been recommended to me by a few people who know DS. Like your son, DS loves spore, has all the add ons and has played it alot.
http://www.thinkwithportals.com/ This is info on Portal 2. The origianl is cheaper now that the "2" is out.

Shari
Mom to DS 10, DS 11, DS 13
Ability doesn't make us, Choices do!