If you already have your Sente notes (and perhaps PDFs) in DEVONthink, you can use the DEVONthink ⇄ OmniFocus integration scripts to simply give you links (in the notes of your OF projects/tasks) to DEVONthink records.

I mainly use OF as a kind of scheduling front end to work on projects maintained in DEVONthink. 'Verbs in OmniFocus and nouns in DT' is one way of thinking about it.

(DT is really a better place to store documents and notes than OF – the retrieval is much faster and more flexible. OmniFocus is very good at collecting material, but oddly unenthusiastic about helping you to find it :-)