I've known this guy, friend of a friend, for about 7 years. We have never really spent much 1 on 1 time together, it's always been in a group.
Last night out a couple months back, everyone was a bit drunk, we were sitting together and things got a bit handsy under the table. It didn't last long and we've never spoken about it but we've seen each other since and the sexual chemistry is intense.
ANYWAY, back to the problem. We were both invited to an event a few hundred miles away. I've bought myself a beautiful dress (like, really beautiful. I'm no stunner but when I tried this dress on even I looked in the mirror and thought DAMN I look good!) and some flattering underwear to go with it. Just in case 
It turns out we're both driving down the day before and staying overnight in the hotel prior to the event. Everyone else is driving down on the day. He has asked if I want to have dinner + drinks the night before. I don't want to wear The Sexy Dress because I've saved it for the event. So what do I wear????
Its just an informal dinner in the hotel restaurant and "jeans and a nice top" is my usual go-to which he's seen me in loads of times. I want to dress to impress. Do I get myself another killer dress or stay business-as-usual? I dont want to look like i'm trying too hard. What's casual but sexy at the same time? I'm shit at dressing myself usually. 