I think that in order to get Spider II working with Poseidon, you need to get a specific, older version of Poseidon (v2?) and use an appropriate Spider-compatible keyfile that works with that version.
Of course, registering a new keyfile for Spider is impossible today, so unless you find a used Spider II with a working keyfile provided + the old Spider-compatible version of Poseidon, you are out of luck.
Today, there is absolutely no sense in buying a brand new Spider card. I'd be surprised if Elbox actually still sell it, since there is no possibility of actually using the card...unless Elbox release their own custom USB stack or something.
