DP1 vs DP1s vs DP1x?

IMO the DP1 Merrill is unmatched in IQ.  LOVE it.  But can't afford it until like 2015 when I can get a used one! lol

Anyway, for now I want to buy a DP1, DP1s, or DP1x used to a) display on my shelf and b) go outside and take awesome daylight photos on occasion.

Question, what is the difference between them?  Which has the best IQ?  Thanks a lot!

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