Both Zin and 1924 Main are close by. Of the two, I would say Zin was a little more romantic. We went there on my birthday a couple of weeks ago and it was really good. They have a special "cosmopolitan" every night where the bartender makes her own infused vodkas, and I had the Ruby Red that night... it was fantastic. We had scallops for our appetizer and they were truly amazing. Everything else was great as well. My favorite part... the free little chocolate they gave us after we sat there for so long!! The regular dessert menu is lacking though... I would head next door to 1924 Main for desserts or earlier in the day, head to Christopher Elbow Chocolates and save those for the hotel room!
1924 Main is excellent as well... they have a 3-course prix fixe menu every night and truly the most inventive desserts in KC that I've run across. They have won us over on many, many foods that we previously thought we didn't like!
bluestem is always highly recommended, although I did not enjoy my one meal that I've had there as much, but it is romantic! They've had a lot of write-ups in magazines, and it is often touted the best restaurant in KC. They do have a tasting menu, however, that I think we would be fun on a romantic night. The desserts here are very good as well.
Let us know where you end up! Have fun!