Class and Level Geekery VIII (spoilers ahoy!)

[Lothston]

If there's anything which would count as "expanded core", surely it would be the SRD? It's core not because it's applicable to everyone, but because it's near-universally available.

No, the SRD are only the rules which have been released under the Open Game license. They're a motley mix of core and obscure supplements, such as the Expanded Psionics Handbook, Deities and Demigods, Unearthed Arcana etc., some of which are even 3.0 (Deities).