Great suggestion about Kat - she is way too much fun in the sack AND she is an intelligent, educated conversationalist.
Another possible recommendation is Felicity Scott. I haven't gone out for dinner with her, but I could easily see myself doing so.
http://ms.felicityscott.com
Conversationally, ask yourself who you'd rather chat with. If it's someone like Carl Sagan or Richard Dawkins, Kat is your choice. If it's Leonard Cohen or Joni Mitchell, then Felicity. (My apologies to Kat and Felicity if I've pigeonholed them - just trying to give a quick reference.)
Please don't think about sex with any of those other people though.
Another Indy I had a great conversation with was Miss Jane Woods - now retired I believe. I thought she had a Scarlet Johansson (sp?) quality - which works both during and after conversation.
Just a thought: imagine if there were Johns for intellectuals? There would be review boards, and we would rate them based on their logic, rigor, persuasive skills, etc. Check out the massive vocabulary on her!