The 600 Series from 98-00 were all CE models, with the option of deleting the electronics, the cutaway or both. The designation on the label was still a CE. The current 600 Series has non-cutaway pure acoustic models and non-cutaways with electronics, as well the CEs, but a model with a cutaway and without electronics could be labeled either way (a 6XX with a cutaway option, or a 6XXCE, delete electronics).
The Jumbo (still available as a BTO), has a 17" lower bout, the GS is slightly larger than the GA (16.25" vs 16"), but the GO is closest, in terms of lower bout dimensions (16.75"), to the Jumbo.