Why take a body? Why make a Ring?

[Raynor]

Was Sauron's native power increased by the fact of the Ring? That is, let's say Sauron = 7 and the Ring = 6; does it make sense within the way LotR was sub-created that Sauron increases, by virtue of the Ring, from a 7 to a 10? ...such that even while dispossessed of the Ring, he functions effectively as a 5 (instead of the expected 7-6=1)? (the numbers are of course arbitrary and meant strictly for illustration).?

To address both bolded issues, I think that Letter #131 comes in handy :

While he wore it, his power on earth was actually enhanced. But even if he did not wear it, that power existed and was in 'rapport' with himself: he was not 'diminished'.

this source also reinforces the previous argument various posters have made about Sauron's intent with the ring:

This was the essential weakness [the possessing of the ring by someone else] he had introduced into his situation in his effort (largely unsuccessful) to enslave the Elves, and in his desire to establish a control over the minds and wills of his servants.

Edit:
Concerning the statement in letter #131 that Sauron was not diminished without the ring, it seems to be at odds with LotR:

Originally Posted by Shadow of the past, FotR

This is the One Ring that he lost many ages ago, to the great weakening of his power.

unless the first quote means that the _potential_ power was not dimished.