Hi
If i follow you through correctly you want what i am endevouring to do....
Well I have been informed by support you can set each site to have their own independent prices for example item 1 = $10 in us store £ 5 in uk store and say 10 euro in euro store. They are not set to any conversion mode because the prices are set in concrete as it were, they never move. But it is true at the moment support are looking at it because when i change one price in one cart it changes in the other 2 carts. But apparently this should not be the case. Each of the 3 carts can have prices and other things set independently. I myself am anxious to get this sorted and am just processing the us cart orders with my mailing just reaching my customers now! .Here's my link..talk about a sweat job!
http://www.welcomerecordings.com/
Thanks Paul
PS But i don't want to seem negative here with support-they really are trying and do give 110% with any probs to get it sorted....