I might suggest you look at the Marriott Travel Package awards. In most cases, it is by far the best way to get a large number of airline miles from hotel stays.

BTW, I tend to agree with MSPeconomist in terms of picking a secondary or tertiary program. I tend to look at Hilton and Marriott as very similar to each other and thus you won't get as much "diversification" by holding status in both of these programs (versus holding say Hyatt or SPG elite status.) With the number of nights you have, you should easily be able to keep Plat with Marriott plus top tier with Starwood or Hyatt. (And note, I keep PC Plat basically just as sdsearch suggests. Even with less than 6 nights in a PC hotel this year, I have had PC Plat wrapped up since March.)