I've got the 830 and love it. But, I would hate loading it and unloading it on a quilt frame. If I had to do that more than once or twice a month, that would not be fun at all. It's a heavy beast. I would also want to try it out at a dealer's on a frame before purchasing. Have you been able to try it?
If you are able to, I'd say keep your 440 too. You can use it to piece if you have the 820 busy on the frame. Also, you'll need a back-up while the other machine is being serviced.
There is a steep learning curve as this machine is unlike any on the market and can be a challenge to some to learn. I took to it like a fish in water, but I'm pretty computer savy. ;)