I'm sitting at Dynamic Duo, $125, and I don't see anything super-practical that I can reach for that isn't hugely beyond my budget.
How about (suggestion): offer us something in the $50 range as a perk: add a couple rows of enhancement/auction/inspiration inventory, two costume slots, and two character slots.
Or offer tiers (one set of expanders on every level for $30, two for $50, three for $70). Getting people to stretch to 150% or so of their original pledge for something super-practical in-game would give you a bump, I think, it would be minimal work on your side... and it's not like we're not going to give you this money eventually anyway. :)