With D/B you mean the extra PCB that attaches to Gayle?
If so... Then you definitelly can use the Buffered IDE adapter in order to use all 4 drives (using Idefix ofc) but you'll lack the extra speed that Idefix express promises
Why don't you try and find out why your idefix d/b hasn't arrived? It's more expensive than the plain adapter for sure.
Check
here
