NY in September post labor day (or labour day since this is a UK traveler) is always the start of the high season. So $300.00 is a really nothing in the luxury market. You might be able to score some fun funky hotel (Thompson Group, The Standard). Otherwise, check out some other major urban places, like Boston, Chicago, Toronto or dare I even suggest good old Montreal to balance the budget.

Santa Monica.... I personally use The Oceana in Santa Monica for large renovated rooms, but yes you give up the oceanviews. The Shore Hotel also gets a lot of press. I'd take a bungalow room at Fairmont vs Casa Del Mar or Shutters. Some really small rooms at those two hotels. Never had good feedback on Huntley

Maui.... With an FSPP booking i would not shy away from FS Maui in a basic room.