I've done my searches and read some faq's here and elsewhere and there is something that confuses me. I'm playing a sorcerer who is currently level 7 with a 19 charisma. As per Table 3 I am receiving the bonus spells per level in accordance with that charisma. When I put on a charisma enhancing piece of equipment such as a Cloak of the Nymph +1 I gain AND THEN SLEEP I gain an extra first level spell which is also exactly like Table 3 says I would.

Here is where I'm confused: Eagle's Splendor. I've seen this as a recommended spell both in a faq on this site and elsewhere. Why? When I experiment with it I can raise my charisma as high as 26 at the moment which according to Table 3 should give me a bonus 2nd and 3rd level spell. However, this bonus doesn't apply immediately. I assume to get the benefit of this higher charisma you would need to rest which makes sense. But resting causes the effect to wear off and you no longer have the higher charisma and resultant extra spells when you wake up.

So, what's the catch? Why are people recommending Eagle's Splendor? What am I missing? If you cast it later as an extended spell does it last long enough that it's still going when you wake? I wouldn't think it would? I'm confused, any help is appreciated.

On a related subject, I know lots of people leave their charisma at 19. I'd think you want at least a level 28 charisma when equipped. Off the top of my head I know there will be +5 Nymph's cloaks to work with and I'm guessing Sharwyn's belt will be +3 charisma. What other tasty equipment enhancing charisma should I keep my eye out for? Thanks.

If the spell works the same way as in IWD2, its duration is 1h/level. So by level 9 you will keep its bonuses after resting. No idea about equipment, never found any fun in the game.

I believe the Charisma modifier affects the DC for Sorcerer spells. It's also good for Paladins because it affects turning undead and the holy aura.

To the best of my recollections, all spell effects are dispelled when resting (the only exception that comes to mind is Curse) which would explain the Eagle's Splendor wearing off.

Ah. Having the spell to improve DC makes sense. Thanks.

Assuming that charisma does affect a sorcerer's DC, I take it that the relationship would be the same as the other modifier relationships? So, 12-13= +1, 14-15= +2 etc?

I believe that is correct.

I think that the DC of a cast spell is something like 10 + ability bonus + spell's level.

that's corrects, and it uses the mods that Laches pointed out.
Ofcourse you add different modifiers to that as well like spell focus etc.