But you could call the i-Go hardcapped accounts this. You can buy extra "bandwidth" in 512mb or 1gig denominations, but it all has to be done manually and the prices are pretty bad. You're better off with a normal 1G and using the 64kb capped service if you need to right now.
Well, with the 64K the connection seems to go "idle" for short periods of time quite often which tends to get rather annoying, I'm in a 100% signal zone as well.