Home Network with cellular USB modem

My only home internet option is 1.5 Mbps DSL, and I have confirmed with my carrier that they have no intention of doing any upgrades. I saw last week where Sprint will soon have a USB modem with speeds of around 3 Mbps download and about half that on upload. Sprint has an unlimited data plan for $60/month. If I were to go with them for that, I could drop my home phone line, long distance plan, and internet plan, so my net monthly would be decreased, plus my internet could go with me. I could not consolidate under Sprint, though, because I love my iPhone enough to stick it out with the same company giving me slow internet (and unreliable internet, at that) at home. Anyway, I am trying to think through how this would work. I have three Macs, an Apple TV, two iPhones, and a Wii. Right now, I have an Airport Extreme Gigabit connected to the DSL and an old Airport Express set up in bridge mode for the G devices. Is there any way to make all of this work while (a) keeping my internet connection active (it's a pain entering my password on Apple TV every time the connection drops) and (b) not having to set up a computer as a home server (if I do that, I would be running at G speed because my only N computer is my MBP). Any ideas?