That dress could take a multitude of jewels, IMO. Pearls are back in vogue, but anything gold or even costume-jeweled bling (czs, rhinestones) are also possible, depending on what you have.
As for hair: I am no expert here. I see designers on reality shows choose updos when they want to show off a neckline, so there's an argument for exposing your neck. But long, lush, swingy hair has a super sexy quotient. Duchess Kate wears her hair down a lot with formal gowns, so I think this dress could take either.
One last thought: While I admire and identify with amping up the desireability quotient in a relationship (plus it's just fun), this whole discussion has made me think about the connection between relationships and clothes. I am not suggesting anything about your relationship here--I certainly don't know you--but since we talk a lot on this forum about the language we use to discuss women, body issues, and clothing, I was thinking we might also apply that awareness to the language we use to describe clothing and relationships. While I am sure we can find plenty of studies linking the two, obviously relationships are a lot more complex. I hope you have a really fun night; your "sexy" knocks it out of the park!
