[Zigûr]

Originally Posted by Puddleglum

I'm not sure that "amplified" is the best word - "focused" may be more applicable.

I've often perceived the qualities of the One Ring this way as well; perhaps it's worth remembering Galadriel's comments to Frodo: "Before you could use that power you would need to become far stronger, and to train your will to the domination of others." (The Lord of the Rings p. 357)
The greatest power of the One Ring was, evidently, its capacity for enabling the exertion of one's own will over the wills of others, to command and be obeyed. Apparently this was not especially necessary for beings of weak will and evil nature, such as Orcs and Trolls, but was invaluable for the domination of other beings. See for instance Sauron in Númenor: "He naturally had the One Ring, and so very soon dominated the minds and wills of most of the Númenóreans." (Letter 211) The Ring is also described in said Letter as the object "upon which his power of dominating minds now largely depends."
Saruman's Voice seemingly possessed an equivalent effect without the need of Rings, but evidently the One would have provided a serious enhancement to his strength in that regard. Certainly Saruman was seeking the One with great fervour, which would suggest to me that he desired its powers specifically, as well as, apparently, denying its access and use to Sauron who would seemingly have been able to eliminate this budding rival for power just as he could have dealt with the rest of his enemies. Gandalf claims that "Isengard cannot fight Mordor, unless Saruman first obtains the Ring." (LR p.486)

Originally Posted by Ardent

I think Saruman's ring probably fits Gandalf's description of the lesser rings; an essay in the craft.

I would agree with this sentiment; Saruman's Ring perhaps had some power like a Lesser Ring, but as Professor Tolkien's remarks from the Foreword which I quoted earlier would suggest he had not managed to craft a Great Ring which would truly have been a formidable tool and weapon. When Saruman openly displayed his Ring to Gandalf and described himself as "Saruman Ring-maker" he was already corrupt, and we have seen his capacity in this way as a liar and deceiver. I would perceive this, then, as largely an act of posturing on his part, perhaps to intimidate Gandalf or maybe even in an effort to convince himself that he was more powerful, and more of an equal to Sauron, than he really was. It's worth noting that shortly after describing himself as a Ring-maker and showing off his own Ring he reveals his desire for the One Ring: "Why not? The Ruling Ring? If we could command that, then the power would pass to us." (LR p.253) This would suggest to me that his own efforts were largely unsuccessful, and that perhaps he was attempting to exaggerate his mastery of Ring-lore.