Last time I updated my phone/renewed my contract, I got one of the last plans that have unlimited data. AFAIK, if you get a Blackberry or 'Droid, you're going to get capped on your data plan, and it gets expensive if you go over it. Unlimited is very expensive. Which data networks are available where your new shop is? I recall reading somewhere that tethering your cell phone (using it for a computer's internet access) is generally frowned upon and (you guessed it) more expensive.
I've used Vonage VOPI for years now and have no complaints. The phone number that I have to have for Verizon DSL I use as a fax line. I send/receive maybe two faxes per month, but I think that you still have to have it. I used Vonage to create a virtual number in Maryland for my mother. She calls a local number and it rings here. It runs around $5 per month. Wonder if they couldn't do the same for your old business number AND create a new number for you when you move so you're covering all the bases. Give it a year to get everyone on your new number, then get rid of it. Also, with Vonage you can go online and have all calls forwarded to another number. So, if you're heading out somewhere and expecting a call, simply give them your cell number and not worry about it. You can also set a time (20 seconds, for instance) before it forwards to your cell in case you have someone answering phones when they can. OR, you can set it to ring to up to five different numbers simultaneously so whomever gets it first, gets it. Vonage is very handy, and it's relatively cheap for what it can do.
More spaghetti for the wall.