Some nights, not all, you can win a 4* in USW for slightly less than the Beresford's $87. Would you rather bid up to the Beresford's price for a 4* or pay less for a 3* or Boutique? If you're okay with a Boutique in USW then you should be okay with a 3* as well. The Rex is the 3* that's been reported on Priceline and the Rex is more or less a Boutique. Read the Rex reviews and if it seems acceptable to you then I suggest bidding 3*. If a Boutique has a lower rate than the 3* your bid will be upgraded. Some new 3* hotel other than the Rex could come up, of course, but I don't really see much potential for a disaster, especially as this is just for one night.