When is your stay - is this next week or next month?

If you would have said earlier this month then you could earn the Marriott Megabonus - 25 nights 50K points for a total of 72,500 points which is much nicer than the Hilton points since they have been so harshly devalued

Currently the best you can do is 15 nights for 25k point bonus on Marriott Megabonus for a total of 32,500 for the first 1/2 of your stay

And then see what is offered by Marriott for Summer 2011- The current Megabonus ends April 30th and the next one should start after that.