Hypersmurf
Moderatarrrrh...
Eagle's splendor is an enhancement bonus just like all the other 2nd level stat boosters. It works like an enhancement bonus as if you had a cloak of charisma. Your charisma increases and consequently anything that relies on chr increases with it - bonus spells, DCs, ST, LoH, etc. To do anything else is to institute a house rule.
You've read the spell, I take it?
Referring specifically to the line "Sorcerers and bards who receive eagle's splendor do not gain extra spells, but the save DCs for their spells increase."
-Hyp.