You have two SDKs exposed. Use -D 1,2 or 3,4 to select the right one.
Trial & Error to find "the right one"?
Is there a way to get rid of one of the SDKs instead?
Would this be an "ATI" and an "AMD" one someplace?
Yeah. One is 2.1, ATI namespace, the other is 2.2 through 2.6, AMD namespace. Trial and error to guess which -D to use, but DM lists it on startup. DM is no longer optimized for 2.1, so you want 2.6, which means you really want Catalyst 12.3 which means do not install SDK 2.6 on top of it.
Yay AMD.