Does it have to be Poly? There are other deluxes that are very nice, not as expensive as Poly (Wilderness & Animal Kingdom Lodge come to mind), you may be able to squeeze at least a 6 day trip by opting for one of those.
The Catch-22 for me in your scenario would be, I really don't like the Values. They're cute and kitschy and all that, and I understand their appeal. But I don't like their size, I don't like their lack of amenities. I enjoy spending time enjoying what a resort has to offer. But if I only had a 5 day trip, I'd probably wind up being a park commando to enjoy the parks, affording me little time to lounge at the resort. Which is why I'd first price out Wilderness and/or Animal Kingdom Lodge. If they were not feasible, I'd probably either drop to a moderate, or Swan or Dolphin. Sure S&D don't have the Disney charm so many of us love, but the price and location are both great.