I know this is a loaded question but I need some opinions on whether or not I should buy the Tamron 17-50 2.8 or just stick with my Nikon 18-55? The reason I ask this question......I am going to Cancun & the Yucatan peninsula for my honeymoon the first week of September. We are definitely going to several of the Mayan ruin sites so I know that I need to go wide. Anyway, I have a D200 and my wife-to-be has a D50. Should I buy the Tamron (can't afford the Nikon 17-55) or just be happy with my Nikon 18-55?