I have not previously heard more than a little of Dalek Empire, and my understanding is that it may be fairest to it to treat the entire series as a single continuous story. For that reason, I am activating a manual override of the Selectortron and instead selecting:
Dalek Empire: Invasion of the Daleks
Starring: Sarah Mowat as Susan Mendes, Mark McDonnell as Alby Brook, and Gareth Thomas as Kalendorf
Format: one full-cast CD (or download) with no episode breaks
Silly? No.
Standalone? No. Invasion of the Daleks can be understood without having heard any prior Big Finish audios, but has no ending whatsoever and is obviously just the first episode of a larger story.
Recommended? Not in itself, and I haven't heard the entire story yet.
My reactions to this story contain spoilers for it and for other releases under the Dalek Empire banner.