[HerenIstarion]

Welcome to the Downs, Gildor Inglorion [img]smilies/smile.gif[/img]

Well, let me comment a bit, would you?

when Gandalf broke his staff

It was not a reason of Saruman loosing power, it was a symbolical expression of him being expelled from the order. A staff for a wizard in ME is not a source of power, but kind of a conductor of power inherent to wizard himself. He lost his power because of disharmony with the position natural to him as a maia and as an istar he placed himself in. to quote myself:

(H-I)

Any creature, however powerful it may have been in the beginning, not serving it's creator but itself degenerates step by step and loses the power instead of accumulating it, as the creatures of the good will are always supported (even that they themselves may know it not) by higher power

I still stick to that.

I think Saruman lost all his powers, except for the voice when he was excluded from the high order, and essentially beeing nothing more than an evil human.

Not when he was expelled, but already, for he has left path of wisdom (neither the reason was loss of power, rather an opposite):

(Gandalf at the Council)

White! " he sneered. "It serves as a beginning. White cloth may be dyed. The white page can be overwritten; and the white light can be broken."
' "In which case it is no longer white," said I. "And he that breaks a thing to find out what it is has left the path of wisdom."

the conversation between Gandalf and Saruman occurred long way before Saruman was cast out of Heren Istarion (no pun intended [img]smilies/smile.gif[/img]), but Saruman may be considered as out of it, by his own choice. Afterwards, breaking Saruman’s staff Gandalf just officially confirms the thing already made by the choice of Saruman himself.

He was more than an evil human, he was fallen maia

Had Grima killed him before his staff was
broken (could he?), his spirit would have definitly returned (afto how long???), now I'm not so sure

Staff has nothing to do with it. I can see your point – you are paralleling istari staffs with Sauron's ring, but that’s not correct, for if it was similar kind of artifact, what on earth would Saruman try to forge his own ring for?

(Gandalf at the Council)

'But I rode to the foot of Orthanc, and came to the stair of Saruman and there he met me and led me up to his high chamber. He wore a ring on his finger.

Doesn't one gain power simply by living and learning

One does. But only (look above) when in harmony with what Eru supposed creature to be. Compare with

[quote](Valaquenta)

From splendour he fell through arrogance to contempt for all things save himself, a spirit wasteful and pitiless. Understanding he turned to subtlety in perverting to his own will all that he would use, until he became a liar without shame. He began with the desire of Light, but when he could not possess it for himself alone, he descended through fire and wrath into a great burning, down into Darkness.

(emphasis mine)

Same is applicable to all falling. Saruman starts to weaken as soon as he wishes power for himself.

Gandalfs death experience made him wiser, and therefore more powerful, and more SELF CONFIDENT.

Entirely incorrect. Gandalf’s death experience made him new, reborn. And not self, but Eru-confident, if I am allowed to coin such an adjective.

LoTR is very complicated work, and more you dig in, more you find, But one of the ideas seen with the eye unarmed is Don’t put yourself first, or either you will be dark lord on your own level