I have not had the opportunity to audition Dynaudio speakers. But from all the positive information I have read about the Contour series. I would not believe that the Studio series from Paradigm would even be close to the same league as the contour's. I have auditioned the Paradigm Studio series many times, and think they are an excellent value, and great sounding speaker.
How much better are the Dynaudio's? I would hope a lot better. Are the $5000 better? Diminishing returns on audio equipment is a personal thing. You would have the bragging rights I can say that.
Why are you choosing to go with the Rel R305 subs? I have never auditioned a Rel sub, so I can't comment on them. But it seems like a lot of money for a sub with a 10" driver.
For the $3000 for two Rel's I think I would be looking at JL Audio Fathom or a SVS or HSU sub. Like I said I'm not knocking the Rel I have no knowledge about them. Trying to learn myself.