Bobby Ryan fetched a roster player a prospect and the #9 pick in the entry draft with one year to go.
JVR is very similar to production and value to BR prior to his trade. Look to that as a gauge of value and try again.
Ryan was the comparable I used as well, it was the #10 pick but done over the summer so the pick wasn't set at the time. The Sens finished around 13th overall the previous year, were getting Spezza back from injury while losing Gonchar, Alfredsson and Silfverberg and adding Ryan. The previous year was the shortened season, and they faded towards the end of it so I'm sure that also weighed into their internal evaluation of how the team would do. Anyway, I think with all the factors considered they probably thought of themselves as a playoff team but not a surefire contender - I would think they expected that pick to be in the teens-to-20ish
Silfverberg though was thought of as a good young player with top 6/first line upside in the near future, was 21 at the time and coming of a .4ppg rookie half season and a near ppg AHL half season. (Like Kapanen if he got called up at the deadline and went .4ppg the rest of the way type value)
They also added Noeson, who if I remember right was a prospect they thought would be an NHL defenseman but not a star
Those two adds I think easily bridge the value gap from what they expected that pick to be and #9OA pick, probably more