Crystal: Marketing high-end properties is a kick! A couple of other thoughts for you:
1) You already have some existing residents, invite them to a nice cocktail hour. Let them know you would like to rent to their friends/associates. Offer a referral incentive (free rent, gift card, spa day, housekeeping services, drawing for vacation, etc.) Your goal is to get into this network. Repeat the message regularaly through e-mails (personalized) or flyers (and don't forget your Facebook page).
2) This is a 'high touch' demographic. They want others to do the 'heavy lifting' for them. The idea of touching base with area realtors is awesome. Often they are coming to town on a temporary assignment or don't want to jump immediately into a house. Realtors want to find somewhere to safely 'park' their client while they identify long-term housing. With realtors, maintain a relationship by letting them know what you have, what your Lease terms are (any flexibility?) and the status of any of their referrals.
3) High end advertising -- if your budget allows, consider advertising in sources that appeal to this demographic. We have used sponsorships on public radio as well as 'status' advertising in the local high-end lifestyle magazines with good success.