So there is currently a promo running through 2/17 where you get $50 extra in-store credit when you trade any Wii U, PS3 or Xbox 360 system. This current ad that runs through 2/19 shows a 50% extra in-store credit when you trade any Wii U, PS3 or Xbox 360 system...

Do these offers stack? If so, that's $140 for a 4GB Xbox 360 and I'll definitely do that.